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	$221.88	5.776%	$234.6958	$234.70	$234.70	$234.70
Purchase #2	$205.98	4.313%	$214.8639	$214.86	$214.85	$214.90
Purchase #3	$247.33	3.450%	$255.8629	$255.86	$255.85	$255.90
Purchase #4	$203.60	13.207%	$230.4895	$230.49	$230.50	$230.50
Purchase #5	$168.48	4.266%	$175.6674	$175.67	$175.65	$175.70
Purchase #6	$148.30	7.416%	$159.2979	$159.30	$159.30	$159.30
Purchase #7	$167.32	3.172%	$172.6274	$172.63	$172.65	$172.60
7 purchase totals =	$1,362.89		$1,443.5048	$1,443.51	$1,443.50	$1,443.60