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 $92.63   4.166%   $96.489   $96.49   $96.50   $96.50  
  Purchase #2 $138.98   10.122%   $153.0476   $153.05   $153.05   $153.00  
  Purchase #3 $209.68   4.341%   $218.7822   $218.78   $218.80   $218.80  
  Purchase #4 $80.38   10.411%   $88.7484   $88.75   $88.75   $88.70  
  Purchase #5 $219.52   12.610%   $247.2015   $247.20   $247.20   $247.20  
  Purchase #6 $130.33   11.179%   $144.8996   $144.90   $144.90   $144.90  
  Purchase #7 $53.74   7.506%   $57.7737   $57.77   $57.75   $57.80  
  7 purchase totals = $925.26       $1,006.9420   $1,006.94   $1,006.95   $1,006.90