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 $108.65   7.613%   $116.9215   $116.92   $116.90   $116.90  
  Purchase #2 $162.98   7.858%   $175.787   $175.79   $175.80   $175.80  
  Purchase #3 $236.38   6.167%   $250.9576   $250.96   $250.95   $251.00  
  Purchase #4 $101.88   5.157%   $107.134   $107.13   $107.15   $107.10  
  Purchase #5 $204.78   3.477%   $211.9002   $211.90   $211.90   $211.90  
  Purchase #6 $174.96   6.297%   $185.9772   $185.98   $186.00   $186.00  
  Purchase #7 $145.47   7.871%   $156.9199   $156.92   $156.90   $156.90  
  7 purchase totals = $1,135.10       $1,205.5974   $1,205.60   $1,205.60   $1,205.60