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 $68.87   9.570%   $75.4609   $75.46   $75.45   $75.50  
  Purchase #2 $151.96   9.109%   $165.802   $165.80   $165.80   $165.80  
  Purchase #3 $5.44   9.499%   $5.9567   $5.96   $5.95   $6.00  
  Purchase #4 $226.82   7.753%   $244.4054   $244.41   $244.40   $244.40  
  Purchase #5 $240.84   9.600%   $263.9606   $263.96   $263.95   $264.00  
  Purchase #6 $128.95   13.401%   $146.2306   $146.23   $146.25   $146.20  
  Purchase #7 $101.85   12.275%   $114.3521   $114.35   $114.35   $114.40  
  7 purchase totals = $924.73       $1,016.1683   $1,016.17   $1,016.15   $1,016.30