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	$88.87	13.563%	$100.9234	$100.92	$100.90	$100.90
Purchase #2	$22.89	10.719%	$25.3436	$25.34	$25.35	$25.30
Purchase #3	$44.27	3.717%	$45.9155	$45.92	$45.90	$45.90
Purchase #4	$119.95	7.123%	$128.494	$128.49	$128.50	$128.50
Purchase #5	$225.81	5.595%	$238.4441	$238.44	$238.45	$238.40
Purchase #6	$96.62	3.607%	$100.1051	$100.11	$100.10	$100.10
Purchase #7	$92.28	9.777%	$101.3022	$101.30	$101.30	$101.30
7 purchase totals =	$690.69		$740.5279	$740.52	$740.50	$740.40