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	$40.42	5.443%	$42.6201	$42.62	$42.60	$42.60
Purchase #2	$75.29	6.433%	$80.1334	$80.13	$80.15	$80.10
Purchase #3	$143.30	4.866%	$150.273	$150.27	$150.25	$150.30
Purchase #4	$165.61	3.461%	$171.3418	$171.34	$171.35	$171.30
Purchase #5	$85.46	4.443%	$89.257	$89.26	$89.25	$89.30
Purchase #6	$247.25	3.568%	$256.0719	$256.07	$256.05	$256.10
Purchase #7	$215.92	7.318%	$231.721	$231.72	$231.70	$231.70
7 purchase totals =	$973.25		$1,021.4182	$1,021.41	$1,021.35	$1,021.40