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 $70.35   8.852%   $76.5774   $76.58   $76.60   $76.60  
  Purchase #2 $181.36   12.373%   $203.7997   $203.80   $203.80   $203.80  
  Purchase #3 $58.44   11.266%   $65.0239   $65.02   $65.00   $65.00  
  Purchase #4 $80.90   4.367%   $84.4329   $84.43   $84.45   $84.40  
  Purchase #5 $191.60   12.721%   $215.9734   $215.97   $215.95   $216.00  
  Purchase #6 $184.97   8.656%   $200.981   $200.98   $201.00   $201.00  
  Purchase #7 $100.30   3.369%   $103.6791   $103.68   $103.70   $103.70  
  7 purchase totals = $867.92       $950.4674   $950.46   $950.50   $950.50