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	$49.31	7.543%	$53.0295	$53.03	$53.05	$53.00
Purchase #2	$44.34	3.613%	$45.942	$45.94	$45.95	$45.90
Purchase #3	$198.57	3.808%	$206.1315	$206.13	$206.15	$206.10
Purchase #4	$66.39	7.525%	$71.3858	$71.39	$71.40	$71.40
Purchase #5	$59.29	3.123%	$61.1416	$61.14	$61.15	$61.10
Purchase #6	$62.88	3.618%	$65.155	$65.16	$65.15	$65.20
Purchase #7	$42.99	8.578%	$46.6777	$46.68	$46.70	$46.70
7 purchase totals =	$523.77		$549.4631	$549.47	$549.55	$549.40