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	$152.30	6.307%	$161.9056	$161.91	$161.90	$161.90
Purchase #2	$231.93	9.417%	$253.7708	$253.77	$253.75	$253.80
Purchase #3	$54.30	13.320%	$61.5328	$61.53	$61.55	$61.50
Purchase #4	$90.78	3.327%	$93.8003	$93.80	$93.80	$93.80
Purchase #5	$83.55	7.492%	$89.8096	$89.81	$89.80	$89.80
Purchase #6	$193.88	9.305%	$211.9205	$211.92	$211.90	$211.90
Purchase #7	$145.84	3.564%	$151.0377	$151.04	$151.05	$151.00
7 purchase totals =	$952.58		$1,023.7773	$1,023.78	$1,023.75	$1,023.70