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	$220.84	4.304%	$230.345	$230.35	$230.35	$230.30
Purchase #2	$241.25	7.475%	$259.2834	$259.28	$259.30	$259.30
Purchase #3	$106.58	4.212%	$111.0691	$111.07	$111.05	$111.10
Purchase #4	$84.75	5.198%	$89.1553	$89.16	$89.15	$89.20
Purchase #5	$12.86	12.273%	$14.4383	$14.44	$14.45	$14.40
Purchase #6	$137.51	7.478%	$147.793	$147.79	$147.80	$147.80
Purchase #7	$63.39	12.720%	$71.4532	$71.45	$71.45	$71.50
7 purchase totals =	$867.18		$923.5373	$923.54	$923.55	$923.60