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 $59.42   5.787%   $62.8586   $62.86   $62.85   $62.90  
  Purchase #2 $122.47   6.570%   $130.5163   $130.52   $130.50   $130.50  
  Purchase #3 $216.68   13.370%   $245.6501   $245.65   $245.65   $245.70  
  Purchase #4 $223.40   4.378%   $233.1805   $233.18   $233.20   $233.20  
  Purchase #5 $239.36   6.547%   $255.0309   $255.03   $255.05   $255.00  
  Purchase #6 $62.55   7.304%   $67.1187   $67.12   $67.10   $67.10  
  Purchase #7 $234.75   9.732%   $257.5959   $257.60   $257.60   $257.60  
  7 purchase totals = $1,158.63       $1,251.9510   $1,251.96   $1,251.95   $1,252.00