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 $176.87   9.732%   $194.083   $194.08   $194.10   $194.10  
  Purchase #2 $34.53   4.397%   $36.0483   $36.05   $36.05   $36.00  
  Purchase #3 $93.47   9.188%   $102.058   $102.06   $102.05   $102.10  
  Purchase #4 $96.97   11.114%   $107.7472   $107.75   $107.75   $107.70  
  Purchase #5 $218.98   8.572%   $237.751   $237.75   $237.75   $237.80  
  Purchase #6 $156.38   10.421%   $172.6764   $172.68   $172.70   $172.70  
  Purchase #7 $214.51   7.791%   $231.2225   $231.22   $231.20   $231.20  
  7 purchase totals = $991.71       $1,081.5864   $1,081.59   $1,081.60   $1,081.60