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	$76.38	8.816%	$83.1137	$83.11	$83.10	$83.10
Purchase #2	$222.29	3.139%	$229.2677	$229.27	$229.25	$229.30
Purchase #3	$205.91	5.771%	$217.7931	$217.79	$217.80	$217.80
Purchase #4	$81.65	13.563%	$92.7242	$92.72	$92.70	$92.70
Purchase #5	$29.77	6.698%	$31.764	$31.76	$31.75	$31.80
Purchase #6	$189.79	3.767%	$196.9394	$196.94	$196.95	$196.90
Purchase #7	$223.65	3.251%	$230.9209	$230.92	$230.90	$230.90
7 purchase totals =	$1,029.44		$1,082.5230	$1,082.51	$1,082.45	$1,082.50