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	$97.74	9.573%	$107.0967	$107.10	$107.10	$107.10
Purchase #2	$11.90	4.763%	$12.4668	$12.47	$12.45	$12.50
Purchase #3	$165.86	5.823%	$175.518	$175.52	$175.50	$175.50
Purchase #4	$143.83	5.354%	$151.5307	$151.53	$151.55	$151.50
Purchase #5	$158.45	5.327%	$166.8906	$166.89	$166.90	$166.90
Purchase #6	$50.95	7.743%	$54.8951	$54.90	$54.90	$54.90
Purchase #7	$179.39	7.467%	$192.7851	$192.79	$192.80	$192.80
7 purchase totals =	$808.12		$861.1830	$861.20	$861.20	$861.20