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 $60.62   5.603%   $64.0165   $64.02   $64.00   $64.00  
  Purchase #2 $148.40   5.349%   $156.3379   $156.34   $156.35   $156.30  
  Purchase #3 $246.35   8.224%   $266.6098   $266.61   $266.60   $266.60  
  Purchase #4 $211.35   12.658%   $238.1027   $238.10   $238.10   $238.10  
  Purchase #5 $15.46   5.815%   $16.359   $16.36   $16.35   $16.40  
  Purchase #6 $72.51   6.264%   $77.052   $77.05   $77.05   $77.10  
  Purchase #7 $216.89   4.650%   $226.9754   $226.98   $227.00   $227.00  
  7 purchase totals = $971.58       $1,045.4533   $1,045.46   $1,045.45   $1,045.50