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	$142.79	5.851%	$151.1446	$151.14	$151.15	$151.10
Purchase #2	$127.33	7.786%	$137.2439	$137.24	$137.25	$137.20
Purchase #3	$120.64	11.167%	$134.1119	$134.11	$134.10	$134.10
Purchase #4	$37.88	3.181%	$39.085	$39.09	$39.10	$39.10
Purchase #5	$55.89	5.431%	$58.9254	$58.93	$58.95	$58.90
Purchase #6	$34.59	10.387%	$38.1829	$38.18	$38.20	$38.20
Purchase #7	$13.51	11.737%	$15.0957	$15.10	$15.10	$15.10
7 purchase totals =	$532.63		$573.7894	$573.79	$573.85	$573.70