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	$103.25	8.301%	$111.8208	$111.82	$111.80	$111.80
Purchase #2	$112.37	12.417%	$126.323	$126.32	$126.30	$126.30
Purchase #3	$113.42	5.740%	$119.9303	$119.93	$119.95	$119.90
Purchase #4	$57.63	6.119%	$61.1564	$61.16	$61.15	$61.20
Purchase #5	$236.27	7.693%	$254.4463	$254.45	$254.45	$254.40
Purchase #6	$151.60	10.576%	$167.6332	$167.63	$167.65	$167.60
Purchase #7	$148.62	8.838%	$161.755	$161.76	$161.75	$161.80
7 purchase totals =	$923.16		$1,003.0650	$1,003.07	$1,003.05	$1,003.00