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	$38.56	11.853%	$43.1305	$43.13	$43.15	$43.10
Purchase #2	$12.45	7.638%	$13.4009	$13.40	$13.40	$13.40
Purchase #3	$113.85	4.654%	$119.1486	$119.15	$119.15	$119.10
Purchase #4	$233.80	5.414%	$246.4579	$246.46	$246.45	$246.50
Purchase #5	$205.86	11.333%	$229.1901	$229.19	$229.20	$229.20
Purchase #6	$139.56	4.734%	$146.1668	$146.17	$146.15	$146.20
Purchase #7	$64.53	10.324%	$71.1921	$71.19	$71.20	$71.20
7 purchase totals =	$808.61		$868.6869	$868.69	$868.70	$868.70