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 $183.29   5.852%   $194.0161   $194.02   $194.00   $194.00  
  Purchase #2 $199.94   11.519%   $222.9711   $222.97   $222.95   $223.00  
  Purchase #3 $42.62   4.501%   $44.5383   $44.54   $44.55   $44.50  
  Purchase #4 $125.87   6.187%   $133.6576   $133.66   $133.65   $133.70  
  Purchase #5 $147.47   12.455%   $165.8374   $165.84   $165.85   $165.80  
  Purchase #6 $104.76   8.650%   $113.8217   $113.82   $113.80   $113.80  
  Purchase #7 $159.31   8.298%   $172.5295   $172.53   $172.55   $172.50  
  7 purchase totals = $963.26       $1,047.3717   $1,047.38   $1,047.35   $1,047.30