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 $161.96   7.273%   $173.7394   $173.74   $173.75   $173.70  
  Purchase #2 $213.42   10.264%   $235.3254   $235.33   $235.35   $235.30  
  Purchase #3 $230.67   5.471%   $243.29   $243.29   $243.30   $243.30  
  Purchase #4 $64.92   13.189%   $73.4823   $73.48   $73.50   $73.50  
  Purchase #5 $71.31   10.634%   $78.8931   $78.89   $78.90   $78.90  
  Purchase #6 $160.32   8.829%   $174.4747   $174.47   $174.45   $174.50  
  Purchase #7 $44.34   3.277%   $45.793   $45.79   $45.80   $45.80  
  7 purchase totals = $946.94       $1,024.9979   $1,024.99   $1,025.05   $1,025.00