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 $212.32   9.109%   $231.6602   $231.66   $231.65   $231.70  
  Purchase #2 $88.43   8.852%   $96.2578   $96.26   $96.25   $96.30  
  Purchase #3 $43.43   9.833%   $47.7005   $47.70   $47.70   $47.70  
  Purchase #4 $16.71   6.364%   $17.7734   $17.77   $17.75   $17.80  
  Purchase #5 $138.61   8.694%   $150.6608   $150.66   $150.65   $150.70  
  Purchase #6 $176.47   4.602%   $184.5911   $184.59   $184.60   $184.60  
  Purchase #7 $203.29   6.749%   $217.01   $217.01   $217.00   $217.00  
  7 purchase totals = $879.26       $945.6538   $945.65   $945.60   $945.80