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 $185.44   4.629%   $194.024   $194.02   $194.00   $194.00  
  Purchase #2 $58.56   10.441%   $64.6742   $64.67   $64.65   $64.70  
  Purchase #3 $218.70   3.160%   $225.6109   $225.61   $225.60   $225.60  
  Purchase #4 $170.89   6.421%   $181.8628   $181.86   $181.85   $181.90  
  Purchase #5 $68.79   7.760%   $74.1281   $74.13   $74.15   $74.10  
  Purchase #6 $147.79   11.711%   $165.0977   $165.10   $165.10   $165.10  
  Purchase #7 $75.56   5.373%   $79.6198   $79.62   $79.60   $79.60  
  7 purchase totals = $925.73       $985.0175   $985.01   $984.95   $985.00