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	$28.83	11.518%	$32.1506	$32.15	$32.15	$32.20
Purchase #2	$89.88	13.346%	$101.8754	$101.88	$101.90	$101.90
Purchase #3	$106.27	11.185%	$118.1563	$118.16	$118.15	$118.20
Purchase #4	$247.55	11.664%	$276.4242	$276.42	$276.40	$276.40
Purchase #5	$207.62	4.345%	$216.6411	$216.64	$216.65	$216.60
Purchase #6	$5.33	4.818%	$5.5868	$5.59	$5.60	$5.60
Purchase #7	$247.58	12.810%	$279.295	$279.30	$279.30	$279.30
7 purchase totals =	$933.06		$1,030.1294	$1,030.14	$1,030.15	$1,030.20