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 $168.31   5.863%   $178.178   $178.18   $178.20   $178.20  
  Purchase #2 $238.29   5.597%   $251.6271   $251.63   $251.65   $251.60  
  Purchase #3 $161.31   5.490%   $170.1659   $170.17   $170.15   $170.20  
  Purchase #4 $103.30   6.395%   $109.906   $109.91   $109.90   $109.90  
  Purchase #5 $63.99   13.736%   $72.7797   $72.78   $72.80   $72.80  
  Purchase #6 $234.77   12.114%   $263.21   $263.21   $263.20   $263.20  
  Purchase #7 $88.76   11.466%   $98.9372   $98.94   $98.95   $98.90  
  7 purchase totals = $1,058.73       $1,144.8039   $1,144.82   $1,144.85   $1,144.80