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	$65.90	8.674%	$71.6162	$71.62	$71.60	$71.60
Purchase #2	$170.61	10.638%	$188.7595	$188.76	$188.75	$188.80
Purchase #3	$116.72	13.162%	$132.0827	$132.08	$132.10	$132.10
Purchase #4	$249.75	6.473%	$265.9163	$265.92	$265.90	$265.90
Purchase #5	$146.36	12.868%	$165.1936	$165.19	$165.20	$165.20
Purchase #6	$184.35	8.398%	$199.8317	$199.83	$199.85	$199.80
Purchase #7	$137.73	10.522%	$152.222	$152.22	$152.20	$152.20
7 purchase totals =	$1,071.42		$1,175.6220	$1,175.62	$1,175.60	$1,175.60