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 $206.68   12.790%   $233.1144   $233.11   $233.10   $233.10  
  Purchase #2 $152.26   4.428%   $159.0021   $159.00   $159.00   $159.00  
  Purchase #3 $197.88   4.805%   $207.3881   $207.39   $207.40   $207.40  
  Purchase #4 $43.29   13.204%   $49.006   $49.01   $49.00   $49.00  
  Purchase #5 $102.33   11.436%   $114.0325   $114.03   $114.05   $114.00  
  Purchase #6 $167.89   10.510%   $185.5352   $185.54   $185.55   $185.50  
  Purchase #7 $182.34   10.147%   $200.842   $200.84   $200.85   $200.80  
  7 purchase totals = $1,052.67       $1,148.9203   $1,148.92   $1,148.95   $1,148.80