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	$116.68	9.243%	$127.4647	$127.46	$127.45	$127.50
Purchase #2	$197.42	10.784%	$218.7098	$218.71	$218.70	$218.70
Purchase #3	$131.42	13.219%	$148.7924	$148.79	$148.80	$148.80
Purchase #4	$143.28	6.409%	$152.4628	$152.46	$152.45	$152.50
Purchase #5	$138.98	9.260%	$151.8495	$151.85	$151.85	$151.80
Purchase #6	$146.32	8.616%	$158.9269	$158.93	$158.95	$158.90
Purchase #7	$89.72	13.272%	$101.6276	$101.63	$101.65	$101.60
7 purchase totals =	$963.82		$1,059.8337	$1,059.83	$1,059.85	$1,059.80