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	$200.48	3.759%	$208.016	$208.02	$208.00	$208.00
Purchase #2	$109.48	6.499%	$116.5951	$116.60	$116.60	$116.60
Purchase #3	$8.38	13.833%	$9.5392	$9.54	$9.55	$9.50
Purchase #4	$17.30	8.277%	$18.7319	$18.73	$18.75	$18.70
Purchase #5	$101.64	8.626%	$110.4075	$110.41	$110.40	$110.40
Purchase #6	$99.53	11.791%	$111.2656	$111.27	$111.25	$111.30
Purchase #7	$148.44	6.797%	$158.5295	$158.53	$158.55	$158.50
7 purchase totals =	$685.25		$733.0848	$733.10	$733.10	$733.00