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	$196.48	8.475%	$213.1317	$213.13	$213.15	$213.10
Purchase #2	$106.25	3.429%	$109.8933	$109.89	$109.90	$109.90
Purchase #3	$148.88	7.191%	$159.586	$159.59	$159.60	$159.60
Purchase #4	$107.93	3.305%	$111.4971	$111.50	$111.50	$111.50
Purchase #5	$200.61	4.322%	$209.2804	$209.28	$209.30	$209.30
Purchase #6	$224.48	11.216%	$249.6577	$249.66	$249.65	$249.70
Purchase #7	$20.39	10.678%	$22.5672	$22.57	$22.55	$22.60
7 purchase totals =	$1,005.02		$1,075.6134	$1,075.62	$1,075.65	$1,075.70