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	$162.60	7.443%	$174.7023	$174.70	$174.70	$174.70
Purchase #2	$227.89	13.424%	$258.482	$258.48	$258.50	$258.50
Purchase #3	$131.63	13.697%	$149.6594	$149.66	$149.65	$149.70
Purchase #4	$140.93	3.700%	$146.1444	$146.14	$146.15	$146.10
Purchase #5	$107.93	7.512%	$116.0377	$116.04	$116.05	$116.00
Purchase #6	$78.40	13.812%	$89.2286	$89.23	$89.25	$89.20
Purchase #7	$190.48	12.513%	$214.3148	$214.31	$214.30	$214.30
7 purchase totals =	$1,039.86		$1,148.5692	$1,148.56	$1,148.60	$1,148.50