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 $87.33   5.285%   $91.9454   $91.95   $91.95   $91.90  
  Purchase #2 $218.69   4.770%   $229.1215   $229.12   $229.10   $229.10  
  Purchase #3 $131.36   3.143%   $135.4886   $135.49   $135.50   $135.50  
  Purchase #4 $68.41   6.645%   $72.9558   $72.96   $72.95   $73.00  
  Purchase #5 $235.58   3.797%   $244.525   $244.53   $244.55   $244.50  
  Purchase #6 $207.81   7.467%   $223.3272   $223.33   $223.35   $223.30  
  Purchase #7 $218.33   6.169%   $231.7988   $231.80   $231.80   $231.80  
  7 purchase totals = $1,167.51       $1,229.1623   $1,229.18   $1,229.20   $1,229.10