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 $118.96   6.321%   $126.4795   $126.48   $126.50   $126.50  
  Purchase #2 $69.75   5.122%   $73.3226   $73.32   $73.30   $73.30  
  Purchase #3 $153.54   12.652%   $172.9659   $172.97   $172.95   $173.00  
  Purchase #4 $47.85   12.374%   $53.771   $53.77   $53.75   $53.80  
  Purchase #5 $97.41   9.139%   $106.3123   $106.31   $106.30   $106.30  
  Purchase #6 $190.91   9.830%   $209.6765   $209.68   $209.70   $209.70  
  Purchase #7 $196.54   7.586%   $211.4495   $211.45   $211.45   $211.40  
  7 purchase totals = $874.96       $953.9773   $953.98   $953.95   $954.00