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	$29.74	11.817%	$33.2544	$33.25	$33.25	$33.30
Purchase #2	$145.60	11.117%	$161.7864	$161.79	$161.80	$161.80
Purchase #3	$193.82	3.516%	$200.6347	$200.63	$200.65	$200.60
Purchase #4	$80.46	12.367%	$90.4105	$90.41	$90.40	$90.40
Purchase #5	$175.41	13.422%	$198.9535	$198.95	$198.95	$199.00
Purchase #6	$175.64	7.533%	$188.871	$188.87	$188.85	$188.90
Purchase #7	$175.62	6.622%	$187.2496	$187.25	$187.25	$187.20
7 purchase totals =	$976.29		$1,061.1601	$1,061.15	$1,061.15	$1,061.20