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	$228.59	6.195%	$242.7512	$242.75	$242.75	$242.80
Purchase #2	$48.86	6.866%	$52.2147	$52.21	$52.20	$52.20
Purchase #3	$45.40	6.285%	$48.2534	$48.25	$48.25	$48.30
Purchase #4	$93.39	10.543%	$103.2361	$103.24	$103.25	$103.20
Purchase #5	$80.82	3.191%	$83.399	$83.40	$83.40	$83.40
Purchase #6	$73.53	13.401%	$83.3838	$83.38	$83.40	$83.40
Purchase #7	$104.48	12.252%	$117.2809	$117.28	$117.30	$117.30
7 purchase totals =	$675.07		$730.5191	$730.51	$730.55	$730.60