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	$241.64	7.256%	$259.1734	$259.17	$259.15	$259.20
Purchase #2	$17.99	3.345%	$18.5918	$18.59	$18.60	$18.60
Purchase #3	$33.65	13.227%	$38.1009	$38.10	$38.10	$38.10
Purchase #4	$61.79	10.815%	$68.4726	$68.47	$68.45	$68.50
Purchase #5	$195.48	3.826%	$202.9591	$202.96	$202.95	$203.00
Purchase #6	$83.72	8.363%	$90.7215	$90.72	$90.70	$90.70
Purchase #7	$100.62	10.610%	$111.2958	$111.30	$111.30	$111.30
7 purchase totals =	$734.89		$789.3151	$789.31	$789.25	$789.40