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	$137.96	9.508%	$151.0772	$151.08	$151.10	$151.10
Purchase #2	$35.62	5.130%	$37.4473	$37.45	$37.45	$37.40
Purchase #3	$191.65	4.292%	$199.8756	$199.88	$199.90	$199.90
Purchase #4	$242.81	13.615%	$275.8686	$275.87	$275.85	$275.90
Purchase #5	$78.88	9.198%	$86.1354	$86.14	$86.15	$86.10
Purchase #6	$55.86	11.498%	$62.2828	$62.28	$62.30	$62.30
Purchase #7	$146.37	8.117%	$158.2509	$158.25	$158.25	$158.30
7 purchase totals =	$889.15		$970.9378	$970.95	$971.00	$971.00