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	$50.86	5.252%	$53.5312	$53.53	$53.55	$53.50
Purchase #2	$64.45	4.364%	$67.2626	$67.26	$67.25	$67.30
Purchase #3	$230.82	7.110%	$247.2313	$247.23	$247.25	$247.20
Purchase #4	$134.30	6.377%	$142.8643	$142.86	$142.85	$142.90
Purchase #5	$214.76	12.380%	$241.3473	$241.35	$241.35	$241.30
Purchase #6	$145.76	13.490%	$165.423	$165.42	$165.40	$165.40
Purchase #7	$13.56	8.562%	$14.721	$14.72	$14.70	$14.70
7 purchase totals =	$854.51		$932.3807	$932.37	$932.35	$932.30