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	$22.38	7.411%	$24.0386	$24.04	$24.05	$24.00
Purchase #2	$81.77	9.240%	$89.3255	$89.33	$89.35	$89.30
Purchase #3	$117.62	8.692%	$127.8435	$127.84	$127.85	$127.80
Purchase #4	$76.56	12.325%	$85.996	$86.00	$86.00	$86.00
Purchase #5	$100.27	9.792%	$110.0884	$110.09	$110.10	$110.10
Purchase #6	$51.74	10.749%	$57.3015	$57.30	$57.30	$57.30
Purchase #7	$241.64	7.121%	$258.8472	$258.85	$258.85	$258.80
7 purchase totals =	$691.98		$753.4407	$753.45	$753.50	$753.30