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 $92.74   3.717%   $96.1871   $96.19   $96.20   $96.20  
  Purchase #2 $156.31   4.238%   $162.9344   $162.93   $162.95   $162.90  
  Purchase #3 $142.53   5.679%   $150.6243   $150.62   $150.60   $150.60  
  Purchase #4 $223.83   9.620%   $245.3624   $245.36   $245.35   $245.40  
  Purchase #5 $203.29   3.664%   $210.7385   $210.74   $210.75   $210.70  
  Purchase #6 $73.29   13.847%   $83.4385   $83.44   $83.45   $83.40  
  Purchase #7 $194.79   6.293%   $207.0481   $207.05   $207.05   $207.00  
  7 purchase totals = $1,086.78       $1,156.3333   $1,156.33   $1,156.35   $1,156.20