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	$231.42	9.468%	$253.3308	$253.33	$253.35	$253.30
Purchase #2	$85.44	4.251%	$89.0721	$89.07	$89.05	$89.10
Purchase #3	$139.55	4.659%	$146.0516	$146.05	$146.05	$146.10
Purchase #4	$5.67	3.253%	$5.8544	$5.85	$5.85	$5.90
Purchase #5	$99.31	12.580%	$111.8032	$111.80	$111.80	$111.80
Purchase #6	$220.43	13.750%	$250.7391	$250.74	$250.75	$250.70
Purchase #7	$187.40	9.364%	$204.9481	$204.95	$204.95	$204.90
7 purchase totals =	$969.22		$1,061.7993	$1,061.79	$1,061.80	$1,061.80