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 $37.96   8.871%   $41.3274   $41.33   $41.35   $41.30  
  Purchase #2 $169.48   13.416%   $192.2174   $192.22   $192.20   $192.20  
  Purchase #3 $110.33   9.432%   $120.7363   $120.74   $120.75   $120.70  
  Purchase #4 $237.91   7.115%   $254.8373   $254.84   $254.85   $254.80  
  Purchase #5 $163.35   11.828%   $182.671   $182.67   $182.65   $182.70  
  Purchase #6 $193.86   3.160%   $199.986   $199.99   $200.00   $200.00  
  Purchase #7 $119.84   11.686%   $133.8445   $133.84   $133.85   $133.80  
  7 purchase totals = $1,032.73       $1,125.6199   $1,125.63   $1,125.65   $1,125.50