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	$221.77	12.849%	$250.2652	$250.27	$250.25	$250.30
Purchase #2	$13.27	11.529%	$14.7999	$14.80	$14.80	$14.80
Purchase #3	$112.44	13.697%	$127.8409	$127.84	$127.85	$127.80
Purchase #4	$88.49	12.197%	$99.2831	$99.28	$99.30	$99.30
Purchase #5	$15.54	3.178%	$16.0339	$16.03	$16.05	$16.00
Purchase #6	$30.89	11.443%	$34.4247	$34.42	$34.40	$34.40
Purchase #7	$231.46	9.629%	$253.7473	$253.75	$253.75	$253.70
7 purchase totals =	$713.86		$796.3950	$796.39	$796.40	$796.30