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	$98.69	4.844%	$103.4705	$103.47	$103.45	$103.50
Purchase #2	$209.57	7.659%	$225.621	$225.62	$225.60	$225.60
Purchase #3	$142.41	13.627%	$161.8162	$161.82	$161.80	$161.80
Purchase #4	$68.59	11.606%	$76.5506	$76.55	$76.55	$76.60
Purchase #5	$106.78	6.111%	$113.3053	$113.31	$113.30	$113.30
Purchase #6	$217.67	13.743%	$247.5844	$247.58	$247.60	$247.60
Purchase #7	$138.30	9.335%	$151.2103	$151.21	$151.20	$151.20
7 purchase totals =	$982.01		$1,079.5583	$1,079.56	$1,079.50	$1,079.60