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	$192.95	5.332%	$203.2381	$203.24	$203.25	$203.20
Purchase #2	$147.56	3.680%	$152.9902	$152.99	$153.00	$153.00
Purchase #3	$70.66	11.766%	$78.9739	$78.97	$78.95	$79.00
Purchase #4	$173.49	4.188%	$180.7558	$180.76	$180.75	$180.80
Purchase #5	$121.38	7.464%	$130.4398	$130.44	$130.45	$130.40
Purchase #6	$145.96	6.499%	$155.4459	$155.45	$155.45	$155.40
Purchase #7	$97.43	3.477%	$100.8176	$100.82	$100.80	$100.80
7 purchase totals =	$949.43		$1,002.6613	$1,002.67	$1,002.65	$1,002.60