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 $68.45   10.300%   $75.5004   $75.50   $75.50   $75.50  
  Purchase #2 $211.61   10.717%   $234.2882   $234.29   $234.30   $234.30  
  Purchase #3 $102.44   7.273%   $109.8905   $109.89   $109.90   $109.90  
  Purchase #4 $41.50   9.301%   $45.3599   $45.36   $45.35   $45.40  
  Purchase #5 $80.62   11.266%   $89.7026   $89.70   $89.70   $89.70  
  Purchase #6 $107.45   5.373%   $113.2233   $113.22   $113.20   $113.20  
  Purchase #7 $83.84   9.674%   $91.9507   $91.95   $91.95   $92.00  
  7 purchase totals = $695.91       $759.9156   $759.91   $759.90   $760.00