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 $212.98   10.774%   $235.9265   $235.93   $235.95   $235.90  
  Purchase #2 $139.52   11.454%   $155.5006   $155.50   $155.50   $155.50  
  Purchase #3 $41.60   6.506%   $44.3065   $44.31   $44.30   $44.30  
  Purchase #4 $214.39   5.860%   $226.9533   $226.95   $226.95   $227.00  
  Purchase #5 $208.96   10.472%   $230.8423   $230.84   $230.85   $230.80  
  Purchase #6 $197.59   6.342%   $210.1212   $210.12   $210.10   $210.10  
  Purchase #7 $177.70   7.873%   $191.6903   $191.69   $191.70   $191.70  
  7 purchase totals = $1,192.74       $1,295.3407   $1,295.34   $1,295.35   $1,295.30