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 $102.96   10.664%   $113.9397   $113.94   $113.95   $113.90  
  Purchase #2 $46.92   13.617%   $53.3091   $53.31   $53.30   $53.30  
  Purchase #3 $121.41   9.671%   $133.1516   $133.15   $133.15   $133.20  
  Purchase #4 $234.26   4.655%   $245.1648   $245.16   $245.15   $245.20  
  Purchase #5 $57.74   10.444%   $63.7704   $63.77   $63.75   $63.80  
  Purchase #6 $219.67   12.425%   $246.964   $246.96   $246.95   $247.00  
  Purchase #7 $197.93   11.405%   $220.5039   $220.50   $220.50   $220.50  
  7 purchase totals = $980.89       $1,076.8035   $1,076.79   $1,076.75   $1,076.90