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	$121.81	4.722%	$127.5619	$127.56	$127.55	$127.60
Purchase #2	$169.62	13.874%	$193.1531	$193.15	$193.15	$193.20
Purchase #3	$179.57	9.657%	$196.9111	$196.91	$196.90	$196.90
Purchase #4	$135.64	3.427%	$140.2884	$140.29	$140.30	$140.30
Purchase #5	$93.50	12.573%	$105.2558	$105.26	$105.25	$105.30
Purchase #6	$196.55	7.149%	$210.6014	$210.60	$210.60	$210.60
Purchase #7	$34.76	10.563%	$38.4317	$38.43	$38.45	$38.40
7 purchase totals =	$931.45		$1,012.2034	$1,012.20	$1,012.20	$1,012.30