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	$203.65	10.442%	$224.9151	$224.92	$224.90	$224.90
Purchase #2	$153.80	12.855%	$173.571	$173.57	$173.55	$173.60
Purchase #3	$52.99	6.283%	$56.3194	$56.32	$56.30	$56.30
Purchase #4	$37.77	12.867%	$42.6299	$42.63	$42.65	$42.60
Purchase #5	$139.62	4.203%	$145.4882	$145.49	$145.50	$145.50
Purchase #6	$39.76	13.822%	$45.2556	$45.26	$45.25	$45.30
Purchase #7	$164.83	11.243%	$183.3618	$183.36	$183.35	$183.40
7 purchase totals =	$792.42		$871.5410	$871.55	$871.50	$871.60