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 $169.26   3.260%   $174.7779   $174.78   $174.80   $174.80  
  Purchase #2 $145.82   12.159%   $163.5503   $163.55   $163.55   $163.60  
  Purchase #3 $36.76   4.690%   $38.484   $38.48   $38.50   $38.50  
  Purchase #4 $119.35   6.321%   $126.8941   $126.89   $126.90   $126.90  
  Purchase #5 $191.79   13.418%   $217.5244   $217.52   $217.50   $217.50  
  Purchase #6 $149.86   6.852%   $160.1284   $160.13   $160.15   $160.10  
  Purchase #7 $250.69   8.826%   $272.8159   $272.82   $272.80   $272.80  
  7 purchase totals = $1,063.53       $1,154.1750   $1,154.17   $1,154.20   $1,154.20