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 $87.91   5.502%   $92.7468   $92.75   $92.75   $92.70  
  Purchase #2 $132.29   3.819%   $137.3422   $137.34   $137.35   $137.30  
  Purchase #3 $118.85   8.276%   $128.686   $128.69   $128.70   $128.70  
  Purchase #4 $44.96   8.426%   $48.7483   $48.75   $48.75   $48.70  
  Purchase #5 $212.92   3.538%   $220.4531   $220.45   $220.45   $220.50  
  Purchase #6 $96.70   5.542%   $102.0591   $102.06   $102.05   $102.10  
  Purchase #7 $33.93   13.414%   $38.4814   $38.48   $38.50   $38.50  
  7 purchase totals = $727.56       $768.5169   $768.52   $768.55   $768.50