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	$49.30	7.779%	$53.135	$53.14	$53.15	$53.10
Purchase #2	$147.55	13.230%	$167.0709	$167.07	$167.05	$167.10
Purchase #3	$44.84	5.392%	$47.2578	$47.26	$47.25	$47.30
Purchase #4	$199.58	3.648%	$206.8607	$206.86	$206.85	$206.90
Purchase #5	$164.63	8.217%	$178.1576	$178.16	$178.15	$178.20
Purchase #6	$210.52	6.151%	$223.4691	$223.47	$223.45	$223.50
Purchase #7	$112.56	12.345%	$126.4555	$126.46	$126.45	$126.50
7 purchase totals =	$928.98		$1,002.4066	$1,002.42	$1,002.35	$1,002.60