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	$244.46	10.402%	$269.8887	$269.89	$269.90	$269.90
Purchase #2	$244.40	6.484%	$260.2469	$260.25	$260.25	$260.20
Purchase #3	$33.46	3.134%	$34.5086	$34.51	$34.50	$34.50
Purchase #4	$160.37	5.315%	$168.8937	$168.89	$168.90	$168.90
Purchase #5	$10.80	4.526%	$11.2888	$11.29	$11.30	$11.30
Purchase #6	$163.87	11.416%	$182.5774	$182.58	$182.60	$182.60
Purchase #7	$170.89	6.302%	$181.6595	$181.66	$181.65	$181.70
7 purchase totals =	$1,028.25		$1,109.0636	$1,109.07	$1,109.10	$1,109.10