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	$65.63	8.422%	$71.1574	$71.16	$71.15	$71.20
Purchase #2	$149.62	10.766%	$165.7281	$165.73	$165.75	$165.70
Purchase #3	$104.76	3.402%	$108.3239	$108.32	$108.30	$108.30
Purchase #4	$228.55	11.840%	$255.6103	$255.61	$255.60	$255.60
Purchase #5	$167.49	13.565%	$190.21	$190.21	$190.20	$190.20
Purchase #6	$84.31	12.846%	$95.1405	$95.14	$95.15	$95.10
Purchase #7	$12.71	5.372%	$13.3928	$13.39	$13.40	$13.40
7 purchase totals =	$813.07		$899.5630	$899.56	$899.55	$899.50