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	$65.41	10.267%	$72.1256	$72.13	$72.15	$72.10
Purchase #2	$10.29	4.777%	$10.7816	$10.78	$10.80	$10.80
Purchase #3	$57.65	13.117%	$65.212	$65.21	$65.20	$65.20
Purchase #4	$190.51	13.498%	$216.225	$216.23	$216.25	$216.20
Purchase #5	$34.90	8.110%	$37.7304	$37.73	$37.75	$37.70
Purchase #6	$112.96	4.789%	$118.3697	$118.37	$118.35	$118.40
Purchase #7	$249.42	9.824%	$273.923	$273.92	$273.90	$273.90
7 purchase totals =	$721.14		$794.3673	$794.37	$794.40	$794.30