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 $165.88   7.475%   $178.2795   $178.28   $178.30   $178.30  
  Purchase #2 $162.86   13.521%   $184.8803   $184.88   $184.90   $184.90  
  Purchase #3 $91.33   5.144%   $96.028   $96.03   $96.05   $96.00  
  Purchase #4 $78.90   10.652%   $87.3044   $87.30   $87.30   $87.30  
  Purchase #5 $67.50   13.843%   $76.844   $76.84   $76.85   $76.80  
  Purchase #6 $162.49   4.374%   $169.5973   $169.60   $169.60   $169.60  
  Purchase #7 $203.79   9.468%   $223.0848   $223.08   $223.10   $223.10  
  7 purchase totals = $932.75       $1,016.0183   $1,016.01   $1,016.10   $1,016.00