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 $65.73   5.516%   $69.3557   $69.36   $69.35   $69.40  
  Purchase #2 $213.83   5.764%   $226.1552   $226.16   $226.15   $226.20  
  Purchase #3 $204.72   7.115%   $219.2858   $219.29   $219.30   $219.30  
  Purchase #4 $235.40   7.793%   $253.7447   $253.74   $253.75   $253.70  
  Purchase #5 $128.32   11.872%   $143.5542   $143.55   $143.55   $143.60  
  Purchase #6 $48.91   11.120%   $54.3488   $54.35   $54.35   $54.30  
  Purchase #7 $70.72   9.578%   $77.4936   $77.49   $77.50   $77.50  
  7 purchase totals = $967.63       $1,043.9380   $1,043.94   $1,043.95   $1,044.00