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 $88.52   7.747%   $95.3776   $95.38   $95.40   $95.40  
  Purchase #2 $235.80   3.566%   $244.2086   $244.21   $244.20   $244.20  
  Purchase #3 $223.71   4.306%   $233.343   $233.34   $233.35   $233.30  
  Purchase #4 $212.99   12.206%   $238.9876   $238.99   $239.00   $239.00  
  Purchase #5 $152.51   6.555%   $162.507   $162.51   $162.50   $162.50  
  Purchase #6 $223.25   5.285%   $235.0488   $235.05   $235.05   $235.00  
  Purchase #7 $109.32   6.773%   $116.7242   $116.72   $116.70   $116.70  
  7 purchase totals = $1,246.10       $1,326.1968   $1,326.20   $1,326.20   $1,326.10