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	$50.49	10.513%	$55.798	$55.80	$55.80	$55.80
Purchase #2	$31.65	10.791%	$35.0654	$35.07	$35.05	$35.10
Purchase #3	$228.25	8.143%	$246.8364	$246.84	$246.85	$246.80
Purchase #4	$79.77	12.472%	$89.7189	$89.72	$89.70	$89.70
Purchase #5	$91.72	5.238%	$96.5243	$96.52	$96.50	$96.50
Purchase #6	$121.52	7.385%	$130.4943	$130.49	$130.50	$130.50
Purchase #7	$64.32	11.597%	$71.7792	$71.78	$71.80	$71.80
7 purchase totals =	$667.72		$726.2165	$726.22	$726.20	$726.20