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 $92.98   11.611%   $103.7759   $103.78   $103.80   $103.80  
  Purchase #2 $225.32   5.346%   $237.3656   $237.37   $237.35   $237.40  
  Purchase #3 $247.51   3.424%   $255.9847   $255.98   $256.00   $256.00  
  Purchase #4 $168.74   10.324%   $186.1607   $186.16   $186.15   $186.20  
  Purchase #5 $176.60   10.106%   $194.4472   $194.45   $194.45   $194.40  
  Purchase #6 $111.81   11.315%   $124.4613   $124.46   $124.45   $124.50  
  Purchase #7 $7.57   5.578%   $7.9923   $7.99   $8.00   $8.00  
  7 purchase totals = $1,030.53       $1,110.1877   $1,110.19   $1,110.20   $1,110.30