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	$108.87	9.732%	$119.4652	$119.47	$119.45	$119.50
Purchase #2	$9.48	10.841%	$10.5077	$10.51	$10.50	$10.50
Purchase #3	$172.89	13.268%	$195.829	$195.83	$195.85	$195.80
Purchase #4	$79.54	13.377%	$90.1801	$90.18	$90.20	$90.20
Purchase #5	$46.30	6.753%	$49.4266	$49.43	$49.45	$49.40
Purchase #6	$62.45	3.344%	$64.5383	$64.54	$64.55	$64.50
Purchase #7	$141.45	11.532%	$157.762	$157.76	$157.75	$157.80
7 purchase totals =	$620.98		$687.7089	$687.72	$687.75	$687.70