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	$81.28	6.397%	$86.4795	$86.48	$86.50	$86.50
Purchase #2	$144.89	9.701%	$158.9458	$158.95	$158.95	$158.90
Purchase #3	$175.89	5.277%	$185.1717	$185.17	$185.15	$185.20
Purchase #4	$208.88	10.362%	$230.5241	$230.52	$230.50	$230.50
Purchase #5	$124.50	8.206%	$134.7165	$134.72	$134.70	$134.70
Purchase #6	$160.30	8.713%	$174.2669	$174.27	$174.25	$174.30
Purchase #7	$118.27	5.142%	$124.3514	$124.35	$124.35	$124.40
7 purchase totals =	$1,014.01		$1,094.4559	$1,094.46	$1,094.40	$1,094.50