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	$233.48	9.433%	$255.5042	$255.50	$255.50	$255.50
Purchase #2	$141.98	7.794%	$153.0459	$153.05	$153.05	$153.00
Purchase #3	$110.41	9.367%	$120.7521	$120.75	$120.75	$120.80
Purchase #4	$139.38	13.410%	$158.0709	$158.07	$158.05	$158.10
Purchase #5	$247.54	4.539%	$258.7758	$258.78	$258.80	$258.80
Purchase #6	$60.51	6.793%	$64.6204	$64.62	$64.60	$64.60
Purchase #7	$89.64	5.526%	$94.5935	$94.59	$94.60	$94.60
7 purchase totals =	$1,022.94		$1,105.3628	$1,105.36	$1,105.35	$1,105.40