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	$52.88	5.110%	$55.5822	$55.58	$55.60	$55.60
Purchase #2	$13.30	10.144%	$14.6492	$14.65	$14.65	$14.60
Purchase #3	$248.80	5.268%	$261.9068	$261.91	$261.90	$261.90
Purchase #4	$59.43	11.484%	$66.2549	$66.25	$66.25	$66.30
Purchase #5	$83.99	6.498%	$89.4477	$89.45	$89.45	$89.40
Purchase #6	$43.47	5.169%	$45.717	$45.72	$45.70	$45.70
Purchase #7	$30.80	11.457%	$34.3288	$34.33	$34.35	$34.30
7 purchase totals =	$532.67		$567.8866	$567.89	$567.90	$567.80