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 $164.92   6.831%   $176.1857   $176.19   $176.20   $176.20  
  Purchase #2 $166.42   8.642%   $180.802   $180.80   $180.80   $180.80  
  Purchase #3 $108.79   4.656%   $113.8553   $113.86   $113.85   $113.90  
  Purchase #4 $105.63   13.748%   $120.152   $120.15   $120.15   $120.20  
  Purchase #5 $205.63   9.146%   $224.4369   $224.44   $224.45   $224.40  
  Purchase #6 $162.92   13.334%   $184.6438   $184.64   $184.65   $184.60  
  Purchase #7 $60.59   4.115%   $63.0833   $63.08   $63.10   $63.10  
  7 purchase totals = $974.90       $1,063.1590   $1,063.16   $1,063.20   $1,063.20