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	$21.33	5.251%	$22.45	$22.45	$22.45	$22.50
Purchase #2	$113.78	12.246%	$127.7135	$127.71	$127.70	$127.70
Purchase #3	$31.42	7.333%	$33.724	$33.72	$33.70	$33.70
Purchase #4	$96.30	8.835%	$104.8081	$104.81	$104.80	$104.80
Purchase #5	$126.84	8.457%	$137.5669	$137.57	$137.55	$137.60
Purchase #6	$169.52	11.211%	$188.5249	$188.52	$188.50	$188.50
Purchase #7	$105.63	5.471%	$111.409	$111.41	$111.40	$111.40
7 purchase totals =	$664.82		$726.1964	$726.19	$726.10	$726.20