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 $85.91   9.705%   $94.2476   $94.25   $94.25   $94.20  
  Purchase #2 $51.32   7.810%   $55.3281   $55.33   $55.35   $55.30  
  Purchase #3 $181.91   9.133%   $198.5238   $198.52   $198.50   $198.50  
  Purchase #4 $64.86   11.747%   $72.4791   $72.48   $72.50   $72.50  
  Purchase #5 $233.51   4.346%   $243.6583   $243.66   $243.65   $243.70  
  Purchase #6 $249.43   11.129%   $277.1891   $277.19   $277.20   $277.20  
  Purchase #7 $237.45   11.489%   $264.7306   $264.73   $264.75   $264.70  
  7 purchase totals = $1,104.39       $1,206.1566   $1,206.16   $1,206.20   $1,206.10