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	$211.28	13.688%	$240.2	$240.20	$240.20	$240.20
Purchase #2	$141.95	7.808%	$153.0335	$153.03	$153.05	$153.00
Purchase #3	$241.68	11.773%	$270.133	$270.13	$270.15	$270.10
Purchase #4	$11.71	4.257%	$12.2085	$12.21	$12.20	$12.20
Purchase #5	$149.74	3.457%	$154.9165	$154.92	$154.90	$154.90
Purchase #6	$183.97	6.707%	$196.3089	$196.31	$196.30	$196.30
Purchase #7	$71.71	6.706%	$76.5189	$76.52	$76.50	$76.50
7 purchase totals =	$1,012.04		$1,103.3193	$1,103.32	$1,103.30	$1,103.20