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	$96.65	9.266%	$105.6056	$105.61	$105.60	$105.60
Purchase #2	$243.71	11.274%	$271.1859	$271.19	$271.20	$271.20
Purchase #3	$61.64	4.444%	$64.3793	$64.38	$64.40	$64.40
Purchase #4	$151.50	12.305%	$170.1421	$170.14	$170.15	$170.10
Purchase #5	$88.25	13.440%	$100.1108	$100.11	$100.10	$100.10
Purchase #6	$104.48	11.748%	$116.7543	$116.75	$116.75	$116.80
Purchase #7	$115.91	9.845%	$127.3213	$127.32	$127.30	$127.30
7 purchase totals =	$862.14		$955.4993	$955.50	$955.50	$955.50