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	$146.31	5.156%	$153.8537	$153.85	$153.85	$153.90
Purchase #2	$22.32	10.771%	$24.7241	$24.72	$24.70	$24.70
Purchase #3	$50.63	6.439%	$53.8901	$53.89	$53.90	$53.90
Purchase #4	$83.57	11.514%	$93.1922	$93.19	$93.20	$93.20
Purchase #5	$38.83	11.390%	$43.2527	$43.25	$43.25	$43.30
Purchase #6	$146.25	5.662%	$154.5307	$154.53	$154.55	$154.50
Purchase #7	$93.79	6.340%	$99.7363	$99.74	$99.75	$99.70
7 purchase totals =	$581.70		$623.1798	$623.17	$623.20	$623.20