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 $72.96   13.514%   $82.8198   $82.82   $82.80   $82.80  
  Purchase #2 $165.84   5.308%   $174.6428   $174.64   $174.65   $174.60  
  Purchase #3 $216.64   5.605%   $228.7827   $228.78   $228.80   $228.80  
  Purchase #4 $106.95   3.169%   $110.3392   $110.34   $110.35   $110.30  
  Purchase #5 $63.91   3.182%   $65.9436   $65.94   $65.95   $65.90  
  Purchase #6 $218.98   12.544%   $246.4489   $246.45   $246.45   $246.40  
  Purchase #7 $183.90   10.126%   $202.5217   $202.52   $202.50   $202.50  
  7 purchase totals = $1,029.18       $1,111.4987   $1,111.49   $1,111.50   $1,111.30