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	$146.35	8.164%	$158.298	$158.30	$158.30	$158.30
Purchase #2	$8.65	3.363%	$8.9409	$8.94	$8.95	$8.90
Purchase #3	$165.90	3.411%	$171.5588	$171.56	$171.55	$171.60
Purchase #4	$151.62	13.279%	$171.7536	$171.75	$171.75	$171.80
Purchase #5	$15.62	11.251%	$17.3774	$17.38	$17.40	$17.40
Purchase #6	$111.49	10.555%	$123.2578	$123.26	$123.25	$123.30
Purchase #7	$65.53	11.263%	$72.9106	$72.91	$72.90	$72.90
7 purchase totals =	$665.16		$724.0971	$724.10	$724.10	$724.20