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 $167.29   6.854%   $178.7561   $178.76   $178.75   $178.80  
  Purchase #2 $192.76   11.166%   $214.2836   $214.28   $214.30   $214.30  
  Purchase #3 $44.56   13.306%   $50.4892   $50.49   $50.50   $50.50  
  Purchase #4 $189.42   3.521%   $196.0895   $196.09   $196.10   $196.10  
  Purchase #5 $152.33   3.689%   $157.9495   $157.95   $157.95   $157.90  
  Purchase #6 $8.95   6.318%   $9.5155   $9.52   $9.50   $9.50  
  Purchase #7 $119.98   6.837%   $128.183   $128.18   $128.20   $128.20  
  7 purchase totals = $875.29       $935.2664   $935.27   $935.30   $935.30