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	$208.72	9.867%	$229.3144	$229.31	$229.30	$229.30
Purchase #2	$63.41	12.222%	$71.16	$71.16	$71.15	$71.20
Purchase #3	$246.39	13.207%	$278.9307	$278.93	$278.95	$278.90
Purchase #4	$97.75	4.109%	$101.7665	$101.77	$101.75	$101.80
Purchase #5	$11.51	8.684%	$12.5095	$12.51	$12.50	$12.50
Purchase #6	$246.87	7.176%	$264.5854	$264.59	$264.60	$264.60
Purchase #7	$54.60	8.521%	$59.2525	$59.25	$59.25	$59.30
7 purchase totals =	$929.25		$1,017.5190	$1,017.52	$1,017.50	$1,017.60