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 $65.34   11.446%   $72.8188   $72.82   $72.80   $72.80  
  Purchase #2 $233.67   12.840%   $263.6732   $263.67   $263.65   $263.70  
  Purchase #3 $183.93   3.729%   $190.7887   $190.79   $190.80   $190.80  
  Purchase #4 $84.93   11.773%   $94.9288   $94.93   $94.95   $94.90  
  Purchase #5 $234.85   3.621%   $243.3539   $243.35   $243.35   $243.40  
  Purchase #6 $155.85   12.227%   $174.9058   $174.91   $174.90   $174.90  
  Purchase #7 $17.46   9.163%   $19.0599   $19.06   $19.05   $19.10  
  7 purchase totals = $976.03       $1,059.5291   $1,059.53   $1,059.50   $1,059.60