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	$31.69	12.131%	$35.5343	$35.53	$35.55	$35.50
Purchase #2	$248.85	10.665%	$275.3899	$275.39	$275.40	$275.40
Purchase #3	$63.72	13.511%	$72.3292	$72.33	$72.35	$72.30
Purchase #4	$15.80	8.282%	$17.1086	$17.11	$17.10	$17.10
Purchase #5	$122.75	8.461%	$133.1359	$133.14	$133.15	$133.10
Purchase #6	$94.49	6.218%	$100.3654	$100.37	$100.35	$100.40
Purchase #7	$65.44	10.280%	$72.1672	$72.17	$72.15	$72.20
7 purchase totals =	$642.74		$706.0305	$706.04	$706.05	$706.00