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	$126.36	3.309%	$130.5413	$130.54	$130.55	$130.50
Purchase #2	$161.68	10.138%	$178.0711	$178.07	$178.05	$178.10
Purchase #3	$123.39	7.647%	$132.8256	$132.83	$132.85	$132.80
Purchase #4	$90.67	9.469%	$99.2555	$99.26	$99.25	$99.30
Purchase #5	$111.93	6.797%	$119.5379	$119.54	$119.55	$119.50
Purchase #6	$144.55	10.820%	$160.1903	$160.19	$160.20	$160.20
Purchase #7	$243.57	9.515%	$266.7457	$266.75	$266.75	$266.70
7 purchase totals =	$1,002.15		$1,087.1674	$1,087.18	$1,087.20	$1,087.10