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	$57.78	8.716%	$62.8161	$62.82	$62.80	$62.80
Purchase #2	$189.67	3.829%	$196.9325	$196.93	$196.95	$196.90
Purchase #3	$52.45	9.777%	$57.578	$57.58	$57.60	$57.60
Purchase #4	$53.88	10.170%	$59.3596	$59.36	$59.35	$59.40
Purchase #5	$240.75	5.370%	$253.6783	$253.68	$253.70	$253.70
Purchase #6	$230.79	7.510%	$248.1223	$248.12	$248.10	$248.10
Purchase #7	$149.93	7.672%	$161.4326	$161.43	$161.45	$161.40
7 purchase totals =	$975.25		$1,039.9194	$1,039.92	$1,039.95	$1,039.90