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	$102.74	8.406%	$111.3763	$111.38	$111.40	$111.40
Purchase #2	$134.68	13.526%	$152.8968	$152.90	$152.90	$152.90
Purchase #3	$94.90	10.873%	$105.2185	$105.22	$105.20	$105.20
Purchase #4	$198.52	9.585%	$217.5481	$217.55	$217.55	$217.50
Purchase #5	$221.89	4.370%	$231.5866	$231.59	$231.60	$231.60
Purchase #6	$112.84	6.453%	$120.1216	$120.12	$120.10	$120.10
Purchase #7	$153.61	7.534%	$165.183	$165.18	$165.20	$165.20
7 purchase totals =	$1,019.18		$1,103.9309	$1,103.94	$1,103.95	$1,103.90