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	$127.64	11.859%	$142.7768	$142.78	$142.80	$142.80
Purchase #2	$10.78	6.864%	$11.5199	$11.52	$11.50	$11.50
Purchase #3	$156.75	9.388%	$171.4657	$171.47	$171.45	$171.50
Purchase #4	$74.64	7.706%	$80.3918	$80.39	$80.40	$80.40
Purchase #5	$23.87	5.460%	$25.1733	$25.17	$25.15	$25.20
Purchase #6	$69.54	3.375%	$71.887	$71.89	$71.90	$71.90
Purchase #7	$81.61	12.616%	$91.9059	$91.91	$91.90	$91.90
7 purchase totals =	$544.83		$595.1204	$595.13	$595.10	$595.20