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	$117.29	5.620%	$123.8817	$123.88	$123.90	$123.90
Purchase #2	$176.47	11.609%	$196.9564	$196.96	$196.95	$197.00
Purchase #3	$79.71	7.741%	$85.8804	$85.88	$85.90	$85.90
Purchase #4	$152.89	8.768%	$166.2954	$166.30	$166.30	$166.30
Purchase #5	$22.74	5.117%	$23.9036	$23.90	$23.90	$23.90
Purchase #6	$145.38	10.664%	$160.8833	$160.88	$160.90	$160.90
Purchase #7	$26.77	5.283%	$28.1843	$28.18	$28.20	$28.20
7 purchase totals =	$721.25		$785.9851	$785.98	$786.05	$786.10