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 $194.66   3.608%   $201.6833   $201.68   $201.70   $201.70  
  Purchase #2 $174.87   12.245%   $196.2828   $196.28   $196.30   $196.30  
  Purchase #3 $174.97   12.708%   $197.2052   $197.21   $197.20   $197.20  
  Purchase #4 $208.68   6.287%   $221.7997   $221.80   $221.80   $221.80  
  Purchase #5 $102.98   10.495%   $113.7878   $113.79   $113.80   $113.80  
  Purchase #6 $152.32   11.476%   $169.8002   $169.80   $169.80   $169.80  
  Purchase #7 $49.55   6.606%   $52.8233   $52.82   $52.80   $52.80  
  7 purchase totals = $1,058.03       $1,153.3823   $1,153.38   $1,153.40   $1,153.40