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 $67.95   9.154%   $74.1701   $74.17   $74.15   $74.20  
  Purchase #2 $197.65   12.422%   $222.2021   $222.20   $222.20   $222.20  
  Purchase #3 $37.37   9.180%   $40.8006   $40.80   $40.80   $40.80  
  Purchase #4 $214.96   12.633%   $242.1159   $242.12   $242.10   $242.10  
  Purchase #5 $246.82   4.598%   $258.1688   $258.17   $258.15   $258.20  
  Purchase #6 $182.93   7.711%   $197.0357   $197.04   $197.05   $197.00  
  Purchase #7 $226.37   6.543%   $241.1814   $241.18   $241.20   $241.20  
  7 purchase totals = $1,174.05       $1,275.6746   $1,275.68   $1,275.65   $1,275.70