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	$226.56	12.778%	$255.5098	$255.51	$255.50	$255.50
Purchase #2	$48.26	3.187%	$49.798	$49.80	$49.80	$49.80
Purchase #3	$92.27	11.366%	$102.7574	$102.76	$102.75	$102.80
Purchase #4	$140.50	4.183%	$146.3771	$146.38	$146.40	$146.40
Purchase #5	$55.43	13.515%	$62.9214	$62.92	$62.90	$62.90
Purchase #6	$70.99	3.717%	$73.6287	$73.63	$73.65	$73.60
Purchase #7	$59.26	3.386%	$61.2665	$61.27	$61.25	$61.30
7 purchase totals =	$693.27		$752.2589	$752.27	$752.25	$752.30