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	$145.50	3.468%	$150.5459	$150.55	$150.55	$150.50
Purchase #2	$170.70	4.645%	$178.629	$178.63	$178.65	$178.60
Purchase #3	$143.90	5.277%	$151.4936	$151.49	$151.50	$151.50
Purchase #4	$132.95	3.425%	$137.5035	$137.50	$137.50	$137.50
Purchase #5	$82.51	9.433%	$90.2932	$90.29	$90.30	$90.30
Purchase #6	$210.89	4.277%	$219.9098	$219.91	$219.90	$219.90
Purchase #7	$160.65	7.685%	$172.996	$173.00	$173.00	$173.00
7 purchase totals =	$1,047.10		$1,101.3710	$1,101.37	$1,101.40	$1,101.30