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 $219.55   8.505%   $238.2227   $238.22   $238.20   $238.20  
  Purchase #2 $181.36   11.273%   $201.8047   $201.80   $201.80   $201.80  
  Purchase #3 $172.25   10.128%   $189.6955   $189.70   $189.70   $189.70  
  Purchase #4 $128.78   6.515%   $137.17   $137.17   $137.15   $137.20  
  Purchase #5 $92.63   4.707%   $96.9901   $96.99   $97.00   $97.00  
  Purchase #6 $200.98   7.493%   $216.0394   $216.04   $216.05   $216.00  
  Purchase #7 $38.75   11.755%   $43.3051   $43.31   $43.30   $43.30  
  7 purchase totals = $1,034.30       $1,123.2275   $1,123.23   $1,123.20   $1,123.20