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 $58.52   7.672%   $63.0097   $63.01   $63.00   $63.00  
  Purchase #2 $234.88   5.813%   $248.5336   $248.53   $248.55   $248.50  
  Purchase #3 $96.94   8.343%   $105.0277   $105.03   $105.05   $105.00  
  Purchase #4 $190.98   8.297%   $206.8256   $206.83   $206.85   $206.80  
  Purchase #5 $245.58   8.351%   $266.0884   $266.09   $266.10   $266.10  
  Purchase #6 $140.74   6.136%   $149.3758   $149.38   $149.40   $149.40  
  Purchase #7 $12.44   13.527%   $14.1228   $14.12   $14.10   $14.10  
  7 purchase totals = $980.08       $1,052.9836   $1,052.99   $1,053.05   $1,052.90