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 $118.84   3.652%   $123.18   $123.18   $123.20   $123.20  
  Purchase #2 $206.72   7.842%   $222.931   $222.93   $222.95   $222.90  
  Purchase #3 $233.87   5.114%   $245.8301   $245.83   $245.85   $245.80  
  Purchase #4 $102.34   13.858%   $116.5223   $116.52   $116.50   $116.50  
  Purchase #5 $145.57   9.256%   $159.044   $159.04   $159.05   $159.00  
  Purchase #6 $23.76   9.485%   $26.0136   $26.01   $26.00   $26.00  
  Purchase #7 $110.27   9.568%   $120.8206   $120.82   $120.80   $120.80  
  7 purchase totals = $941.37       $1,014.3416   $1,014.33   $1,014.35   $1,014.20