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	$107.87	3.593%	$111.7458	$111.75	$111.75	$111.70
Purchase #2	$130.52	8.456%	$141.5568	$141.56	$141.55	$141.60
Purchase #3	$82.31	11.725%	$91.9608	$91.96	$91.95	$92.00
Purchase #4	$18.94	9.444%	$20.7287	$20.73	$20.75	$20.70
Purchase #5	$72.71	7.611%	$78.244	$78.24	$78.25	$78.20
Purchase #6	$231.50	5.666%	$244.6168	$244.62	$244.60	$244.60
Purchase #7	$109.72	7.693%	$118.1608	$118.16	$118.15	$118.20
7 purchase totals =	$753.57		$807.0137	$807.02	$807.00	$807.00