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 $161.52   9.217%   $176.4073   $176.41   $176.40   $176.40  
  Purchase #2 $73.58   3.842%   $76.4069   $76.41   $76.40   $76.40  
  Purchase #3 $243.97   3.130%   $251.6063   $251.61   $251.60   $251.60  
  Purchase #4 $181.84   5.461%   $191.7703   $191.77   $191.75   $191.80  
  Purchase #5 $171.72   7.224%   $184.1251   $184.13   $184.15   $184.10  
  Purchase #6 $91.75   3.390%   $94.8603   $94.86   $94.85   $94.90  
  Purchase #7 $170.69   4.412%   $178.2208   $178.22   $178.20   $178.20  
  7 purchase totals = $1,095.07       $1,153.3970   $1,153.41   $1,153.35   $1,153.40