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 $59.75   4.525%   $62.4537   $62.45   $62.45   $62.50  
  Purchase #2 $193.37   13.531%   $219.5349   $219.53   $219.55   $219.50  
  Purchase #3 $114.52   12.334%   $128.6449   $128.64   $128.65   $128.60  
  Purchase #4 $240.41   11.158%   $267.2349   $267.23   $267.25   $267.20  
  Purchase #5 $188.65   13.864%   $214.8044   $214.80   $214.80   $214.80  
  Purchase #6 $205.60   9.871%   $225.8948   $225.89   $225.90   $225.90  
  Purchase #7 $21.51   12.187%   $24.1314   $24.13   $24.15   $24.10  
  7 purchase totals = $1,023.81       $1,142.6990   $1,142.67   $1,142.75   $1,142.60