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 $83.94   11.345%   $93.463   $93.46   $93.45   $93.50  
  Purchase #2 $240.51   7.384%   $258.2693   $258.27   $258.25   $258.30  
  Purchase #3 $34.66   8.437%   $37.5843   $37.58   $37.60   $37.60  
  Purchase #4 $234.64   4.540%   $245.2927   $245.29   $245.30   $245.30  
  Purchase #5 $147.41   12.668%   $166.0839   $166.08   $166.10   $166.10  
  Purchase #6 $189.94   8.591%   $206.2577   $206.26   $206.25   $206.30  
  Purchase #7 $196.65   3.265%   $203.0706   $203.07   $203.05   $203.10  
  7 purchase totals = $1,127.75       $1,210.0215   $1,210.01   $1,210.00   $1,210.20