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	$123.90	6.548%	$132.013	$132.01	$132.00	$132.00
Purchase #2	$222.56	9.233%	$243.109	$243.11	$243.10	$243.10
Purchase #3	$56.85	4.570%	$59.448	$59.45	$59.45	$59.40
Purchase #4	$14.77	6.647%	$15.7518	$15.75	$15.75	$15.80
Purchase #5	$37.83	5.771%	$40.0132	$40.01	$40.00	$40.00
Purchase #6	$149.29	6.467%	$158.9446	$158.94	$158.95	$158.90
Purchase #7	$167.67	10.464%	$185.215	$185.22	$185.20	$185.20
7 purchase totals =	$772.87		$834.4946	$834.49	$834.45	$834.40