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 $48.45   7.290%   $51.982   $51.98   $52.00   $52.00  
  Purchase #2 $92.65   10.159%   $102.0623   $102.06   $102.05   $102.10  
  Purchase #3 $96.74   11.424%   $107.7916   $107.79   $107.80   $107.80  
  Purchase #4 $193.41   11.419%   $215.4955   $215.50   $215.50   $215.50  
  Purchase #5 $58.50   13.653%   $66.487   $66.49   $66.50   $66.50  
  Purchase #6 $163.95   3.478%   $169.6522   $169.65   $169.65   $169.70  
  Purchase #7 $44.86   12.813%   $50.6079   $50.61   $50.60   $50.60  
  7 purchase totals = $698.56       $764.0785   $764.08   $764.10   $764.20