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 $105.80   13.132%   $119.6937   $119.69   $119.70   $119.70  
  Purchase #2 $155.45   7.621%   $167.2968   $167.30   $167.30   $167.30  
  Purchase #3 $87.75   13.694%   $99.7665   $99.77   $99.75   $99.80  
  Purchase #4 $62.69   4.722%   $65.6502   $65.65   $65.65   $65.70  
  Purchase #5 $235.39   3.427%   $243.4568   $243.46   $243.45   $243.50  
  Purchase #6 $22.99   6.352%   $24.4503   $24.45   $24.45   $24.50  
  Purchase #7 $232.88   3.773%   $241.6666   $241.67   $241.65   $241.70  
  7 purchase totals = $902.95       $961.9809   $961.99   $961.95   $962.20