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 $56.25   10.462%   $62.1349   $62.13   $62.15   $62.10  
  Purchase #2 $156.94   11.734%   $175.3553   $175.36   $175.35   $175.40  
  Purchase #3 $25.61   11.122%   $28.4583   $28.46   $28.45   $28.50  
  Purchase #4 $191.43   11.505%   $213.454   $213.45   $213.45   $213.50  
  Purchase #5 $226.46   8.205%   $245.041   $245.04   $245.05   $245.00  
  Purchase #6 $77.39   4.304%   $80.7209   $80.72   $80.70   $80.70  
  Purchase #7 $173.68   12.745%   $195.8155   $195.82   $195.80   $195.80  
  7 purchase totals = $907.76       $1,000.9799   $1,000.98   $1,000.95   $1,001.00