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	$97.66	7.643%	$105.1242	$105.12	$105.10	$105.10
Purchase #2	$181.66	10.349%	$200.46	$200.46	$200.45	$200.50
Purchase #3	$42.34	12.422%	$47.5995	$47.60	$47.60	$47.60
Purchase #4	$235.78	5.814%	$249.4882	$249.49	$249.50	$249.50
Purchase #5	$118.69	11.678%	$132.5506	$132.55	$132.55	$132.60
Purchase #6	$140.59	12.312%	$157.8994	$157.90	$157.90	$157.90
Purchase #7	$121.41	7.690%	$130.7464	$130.75	$130.75	$130.70
7 purchase totals =	$938.13		$1,023.8683	$1,023.87	$1,023.85	$1,023.90