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	$191.43	8.160%	$207.0507	$207.05	$207.05	$207.10
Purchase #2	$21.44	4.170%	$22.334	$22.33	$22.35	$22.30
Purchase #3	$39.90	13.697%	$45.3651	$45.37	$45.35	$45.40
Purchase #4	$231.88	10.680%	$256.6448	$256.64	$256.65	$256.60
Purchase #5	$35.75	6.145%	$37.9468	$37.95	$37.95	$37.90
Purchase #6	$39.54	13.318%	$44.8059	$44.81	$44.80	$44.80
Purchase #7	$153.45	7.783%	$165.393	$165.39	$165.40	$165.40
7 purchase totals =	$713.39		$779.5403	$779.54	$779.55	$779.50