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	$42.36	12.378%	$47.6033	$47.60	$47.60	$47.60
Purchase #2	$88.68	7.552%	$95.3771	$95.38	$95.40	$95.40
Purchase #3	$95.80	11.846%	$107.1485	$107.15	$107.15	$107.10
Purchase #4	$99.77	4.576%	$104.3355	$104.34	$104.35	$104.30
Purchase #5	$120.58	8.830%	$131.2272	$131.23	$131.25	$131.20
Purchase #6	$10.73	13.204%	$12.1468	$12.15	$12.15	$12.10
Purchase #7	$170.94	11.515%	$190.6237	$190.62	$190.60	$190.60
7 purchase totals =	$628.86		$688.4621	$688.47	$688.50	$688.30