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	$152.95	9.136%	$166.9235	$166.92	$166.90	$166.90
Purchase #2	$101.29	4.452%	$105.7994	$105.80	$105.80	$105.80
Purchase #3	$184.62	8.505%	$200.3219	$200.32	$200.30	$200.30
Purchase #4	$138.71	6.158%	$147.2518	$147.25	$147.25	$147.30
Purchase #5	$113.92	11.605%	$127.1404	$127.14	$127.15	$127.10
Purchase #6	$67.53	5.675%	$71.3623	$71.36	$71.35	$71.40
Purchase #7	$71.50	8.471%	$77.5568	$77.56	$77.55	$77.60
7 purchase totals =	$830.52		$896.3561	$896.35	$896.30	$896.40