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	$222.94	3.269%	$230.2279	$230.23	$230.25	$230.20
Purchase #2	$142.50	6.416%	$151.6428	$151.64	$151.65	$151.60
Purchase #3	$100.86	8.685%	$109.6197	$109.62	$109.60	$109.60
Purchase #4	$244.50	13.523%	$277.5637	$277.56	$277.55	$277.60
Purchase #5	$196.87	10.793%	$218.1182	$218.12	$218.10	$218.10
Purchase #6	$145.66	10.307%	$160.6732	$160.67	$160.65	$160.70
Purchase #7	$55.32	12.594%	$62.287	$62.29	$62.30	$62.30
7 purchase totals =	$1,108.65		$1,210.1325	$1,210.13	$1,210.10	$1,210.10