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 $62.56   3.538%   $64.7734   $64.77   $64.75   $64.80  
  Purchase #2 $243.28   5.496%   $256.6507   $256.65   $256.65   $256.70  
  Purchase #3 $238.33   3.275%   $246.1353   $246.14   $246.15   $246.10  
  Purchase #4 $236.95   3.827%   $246.0181   $246.02   $246.00   $246.00  
  Purchase #5 $53.68   6.245%   $57.0323   $57.03   $57.05   $57.00  
  Purchase #6 $141.89   10.128%   $156.2606   $156.26   $156.25   $156.30  
  Purchase #7 $149.52   10.467%   $165.1703   $165.17   $165.15   $165.20  
  7 purchase totals = $1,126.21       $1,192.0407   $1,192.04   $1,192.00   $1,192.10