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	$63.52	5.546%	$67.0428	$67.04	$67.05	$67.00
Purchase #2	$79.57	12.621%	$89.6125	$89.61	$89.60	$89.60
Purchase #3	$66.47	5.389%	$70.0521	$70.05	$70.05	$70.10
Purchase #4	$97.88	12.341%	$109.9594	$109.96	$109.95	$110.00
Purchase #5	$159.75	11.645%	$178.3529	$178.35	$178.35	$178.40
Purchase #6	$130.85	8.226%	$141.6137	$141.61	$141.60	$141.60
Purchase #7	$29.99	4.803%	$31.4304	$31.43	$31.45	$31.40
7 purchase totals =	$628.03		$688.0638	$688.05	$688.05	$688.10