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 $74.67   8.160%   $80.7631   $80.76   $80.75   $80.80  
  Purchase #2 $188.48   6.672%   $201.0554   $201.06   $201.05   $201.10  
  Purchase #3 $211.88   5.738%   $224.0377   $224.04   $224.05   $224.00  
  Purchase #4 $228.37   6.554%   $243.3374   $243.34   $243.35   $243.30  
  Purchase #5 $62.96   9.370%   $68.8594   $68.86   $68.85   $68.90  
  Purchase #6 $206.52   6.788%   $220.5386   $220.54   $220.55   $220.50  
  Purchase #7 $71.77   3.164%   $74.0408   $74.04   $74.05   $74.00  
  7 purchase totals = $1,044.65       $1,112.6324   $1,112.64   $1,112.65   $1,112.60