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 $153.44   8.613%   $166.6558   $166.66   $166.65   $166.70  
  Purchase #2 $30.39   9.790%   $33.3652   $33.37   $33.35   $33.40  
  Purchase #3 $212.59   11.672%   $237.4035   $237.40   $237.40   $237.40  
  Purchase #4 $169.65   10.300%   $187.124   $187.12   $187.10   $187.10  
  Purchase #5 $240.49   9.217%   $262.656   $262.66   $262.65   $262.70  
  Purchase #6 $227.87   4.113%   $237.2423   $237.24   $237.25   $237.20  
  Purchase #7 $74.51   10.760%   $82.5273   $82.53   $82.55   $82.50  
  7 purchase totals = $1,108.94       $1,206.9741   $1,206.98   $1,206.95   $1,207.00