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	$190.29	5.146%	$200.0823	$200.08	$200.10	$200.10
Purchase #2	$26.70	8.222%	$28.8953	$28.90	$28.90	$28.90
Purchase #3	$193.71	13.194%	$219.2681	$219.27	$219.25	$219.30
Purchase #4	$231.92	13.510%	$263.2524	$263.25	$263.25	$263.30
Purchase #5	$111.67	5.103%	$117.3685	$117.37	$117.35	$117.40
Purchase #6	$31.35	5.768%	$33.1583	$33.16	$33.15	$33.20
Purchase #7	$130.58	13.594%	$148.331	$148.33	$148.35	$148.30
7 purchase totals =	$916.22		$1,010.3559	$1,010.36	$1,010.35	$1,010.50