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	$137.52	4.130%	$143.1996	$143.20	$143.20	$143.20
Purchase #2	$11.85	5.548%	$12.5074	$12.51	$12.50	$12.50
Purchase #3	$185.59	3.613%	$192.2954	$192.30	$192.30	$192.30
Purchase #4	$33.58	9.573%	$36.7946	$36.79	$36.80	$36.80
Purchase #5	$26.90	7.445%	$28.9027	$28.90	$28.90	$28.90
Purchase #6	$136.88	4.855%	$143.5255	$143.53	$143.55	$143.50
Purchase #7	$61.27	5.250%	$64.4867	$64.49	$64.50	$64.50
7 purchase totals =	$593.59		$621.7119	$621.72	$621.75	$621.70