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	$107.29	4.155%	$111.7479	$111.75	$111.75	$111.70
Purchase #2	$174.59	9.137%	$190.5423	$190.54	$190.55	$190.50
Purchase #3	$148.33	10.203%	$163.4641	$163.46	$163.45	$163.50
Purchase #4	$53.82	8.694%	$58.4991	$58.50	$58.50	$58.50
Purchase #5	$49.88	7.485%	$53.6135	$53.61	$53.60	$53.60
Purchase #6	$196.64	10.438%	$217.1653	$217.17	$217.15	$217.20
Purchase #7	$234.73	6.782%	$250.6494	$250.65	$250.65	$250.60
7 purchase totals =	$965.28		$1,045.6816	$1,045.68	$1,045.65	$1,045.60