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	$238.52	4.629%	$249.5611	$249.56	$249.55	$249.60
Purchase #2	$9.91	3.818%	$10.2884	$10.29	$10.30	$10.30
Purchase #3	$53.95	9.434%	$59.0396	$59.04	$59.05	$59.00
Purchase #4	$66.46	7.585%	$71.501	$71.50	$71.50	$71.50
Purchase #5	$133.58	8.741%	$145.2562	$145.26	$145.25	$145.30
Purchase #6	$215.66	3.103%	$222.3519	$222.35	$222.35	$222.40
Purchase #7	$9.78	4.191%	$10.1899	$10.19	$10.20	$10.20
7 purchase totals =	$727.86		$768.1881	$768.19	$768.20	$768.30