Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $181.65   6.862%   $194.1148   $194.11   $194.10   $194.10  
  Purchase #2 $195.98   7.527%   $210.7314   $210.73   $210.75   $210.70  
  Purchase #3 $152.64   8.541%   $165.677   $165.68   $165.70   $165.70  
  Purchase #4 $217.47   11.332%   $242.1137   $242.11   $242.10   $242.10  
  Purchase #5 $220.92   11.560%   $246.4584   $246.46   $246.45   $246.50  
  Purchase #6 $95.43   7.416%   $102.5071   $102.51   $102.50   $102.50  
  Purchase #7 $248.67   10.558%   $274.9246   $274.92   $274.90   $274.90  
  7 purchase totals = $1,312.76       $1,436.5270   $1,436.52   $1,436.50   $1,436.50