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 $187.82   3.413%   $194.2303   $194.23   $194.25   $194.20  
  Purchase #2 $235.97   6.526%   $251.3694   $251.37   $251.35   $251.40  
  Purchase #3 $67.77   11.521%   $75.5778   $75.58   $75.60   $75.60  
  Purchase #4 $60.50   8.333%   $65.5415   $65.54   $65.55   $65.50  
  Purchase #5 $187.27   9.815%   $205.6506   $205.65   $205.65   $205.70  
  Purchase #6 $198.65   11.175%   $220.8491   $220.85   $220.85   $220.80  
  Purchase #7 $165.78   3.731%   $171.9653   $171.97   $171.95   $172.00  
  7 purchase totals = $1,103.76       $1,185.1840   $1,185.19   $1,185.20   $1,185.20