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	$187.93	13.181%	$212.7011	$212.70	$212.70	$212.70
Purchase #2	$204.59	11.219%	$227.543	$227.54	$227.55	$227.50
Purchase #3	$51.35	5.738%	$54.2965	$54.30	$54.30	$54.30
Purchase #4	$61.46	6.544%	$65.4819	$65.48	$65.50	$65.50
Purchase #5	$81.60	12.772%	$92.022	$92.02	$92.00	$92.00
Purchase #6	$117.89	10.522%	$130.2944	$130.29	$130.30	$130.30
Purchase #7	$15.52	11.352%	$17.2818	$17.28	$17.30	$17.30
7 purchase totals =	$720.34		$799.6207	$799.61	$799.65	$799.60