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 $22.59   13.264%   $25.5863   $25.59   $25.60   $25.60  
  Purchase #2 $167.34   11.512%   $186.6042   $186.60   $186.60   $186.60  
  Purchase #3 $36.48   7.818%   $39.332   $39.33   $39.35   $39.30  
  Purchase #4 $233.29   9.811%   $256.1781   $256.18   $256.20   $256.20  
  Purchase #5 $101.86   3.509%   $105.4343   $105.43   $105.45   $105.40  
  Purchase #6 $194.27   9.298%   $212.3332   $212.33   $212.35   $212.30  
  Purchase #7 $199.74   3.824%   $207.3781   $207.38   $207.40   $207.40  
  7 purchase totals = $955.57       $1,032.8462   $1,032.84   $1,032.95   $1,032.80