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 $71.59   7.493%   $76.9542   $76.95   $76.95   $77.00  
  Purchase #2 $120.40   4.299%   $125.576   $125.58   $125.60   $125.60  
  Purchase #3 $85.39   12.646%   $96.1884   $96.19   $96.20   $96.20  
  Purchase #4 $43.31   11.441%   $48.2651   $48.27   $48.25   $48.30  
  Purchase #5 $149.52   6.133%   $158.6901   $158.69   $158.70   $158.70  
  Purchase #6 $38.39   7.829%   $41.3956   $41.40   $41.40   $41.40  
  Purchase #7 $145.91   6.648%   $155.6101   $155.61   $155.60   $155.60  
  7 purchase totals = $654.51       $702.6795   $702.69   $702.70   $702.80