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	$116.47	10.408%	$128.5922	$128.59	$128.60	$128.60
Purchase #2	$116.29	7.788%	$125.3467	$125.35	$125.35	$125.30
Purchase #3	$46.87	11.459%	$52.2408	$52.24	$52.25	$52.20
Purchase #4	$100.30	7.860%	$108.1836	$108.18	$108.20	$108.20
Purchase #5	$234.59	13.483%	$266.2198	$266.22	$266.20	$266.20
Purchase #6	$91.45	4.633%	$95.6869	$95.69	$95.70	$95.70
Purchase #7	$55.42	7.424%	$59.5344	$59.53	$59.55	$59.50
7 purchase totals =	$761.39		$835.8044	$835.80	$835.85	$835.70