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	$120.69	4.458%	$126.0704	$126.07	$126.05	$126.10
Purchase #2	$175.69	13.173%	$198.8336	$198.83	$198.85	$198.80
Purchase #3	$150.57	6.653%	$160.5874	$160.59	$160.60	$160.60
Purchase #4	$152.28	10.502%	$168.2724	$168.27	$168.25	$168.30
Purchase #5	$53.42	4.244%	$55.6871	$55.69	$55.70	$55.70
Purchase #6	$11.43	8.301%	$12.3788	$12.38	$12.40	$12.40
Purchase #7	$103.69	8.739%	$112.7515	$112.75	$112.75	$112.80
7 purchase totals =	$767.77		$834.5812	$834.58	$834.60	$834.70