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	$164.56	8.493%	$178.5361	$178.54	$178.55	$178.50
Purchase #2	$145.78	13.617%	$165.6309	$165.63	$165.65	$165.60
Purchase #3	$233.45	9.539%	$255.7188	$255.72	$255.70	$255.70
Purchase #4	$19.68	3.230%	$20.3157	$20.32	$20.30	$20.30
Purchase #5	$211.55	13.803%	$240.7502	$240.75	$240.75	$240.80
Purchase #6	$199.42	9.389%	$218.1435	$218.14	$218.15	$218.10
Purchase #7	$72.68	9.427%	$79.5315	$79.53	$79.55	$79.50
7 purchase totals =	$1,047.12		$1,158.6267	$1,158.63	$1,158.65	$1,158.50