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	$200.58	3.732%	$208.0656	$208.07	$208.05	$208.10
Purchase #2	$29.45	8.415%	$31.9282	$31.93	$31.95	$31.90
Purchase #3	$123.74	5.577%	$130.641	$130.64	$130.65	$130.60
Purchase #4	$53.71	11.693%	$59.9903	$59.99	$60.00	$60.00
Purchase #5	$173.28	7.258%	$185.8567	$185.86	$185.85	$185.90
Purchase #6	$159.89	7.581%	$172.0113	$172.01	$172.00	$172.00
Purchase #7	$171.98	7.209%	$184.378	$184.38	$184.40	$184.40
7 purchase totals =	$912.63		$972.8711	$972.88	$972.90	$972.90