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	$99.37	4.164%	$103.5078	$103.51	$103.50	$103.50
Purchase #2	$232.33	4.191%	$242.067	$242.07	$242.05	$242.10
Purchase #3	$70.99	9.291%	$77.5857	$77.59	$77.60	$77.60
Purchase #4	$182.79	4.264%	$190.5842	$190.58	$190.60	$190.60
Purchase #5	$216.42	3.369%	$223.7112	$223.71	$223.70	$223.70
Purchase #6	$42.56	7.590%	$45.7903	$45.79	$45.80	$45.80
Purchase #7	$144.40	12.137%	$161.9258	$161.93	$161.95	$161.90
7 purchase totals =	$988.86		$1,045.1720	$1,045.18	$1,045.20	$1,045.20