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 $141.70   6.635%   $151.1018   $151.10   $151.10   $151.10  
  Purchase #2 $163.35   8.144%   $176.6532   $176.65   $176.65   $176.70  
  Purchase #3 $44.65   7.195%   $47.8626   $47.86   $47.85   $47.90  
  Purchase #4 $171.67   10.525%   $189.7383   $189.74   $189.75   $189.70  
  Purchase #5 $108.49   7.547%   $116.6777   $116.68   $116.70   $116.70  
  Purchase #6 $201.72   13.284%   $228.5165   $228.52   $228.50   $228.50  
  Purchase #7 $135.83   6.142%   $144.1727   $144.17   $144.15   $144.20  
  7 purchase totals = $967.41       $1,054.7228   $1,054.72   $1,054.70   $1,054.80