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	$108.82	3.480%	$112.6069	$112.61	$112.60	$112.60
Purchase #2	$205.52	6.852%	$219.6022	$219.60	$219.60	$219.60
Purchase #3	$120.40	6.650%	$128.4066	$128.41	$128.40	$128.40
Purchase #4	$247.76	7.259%	$265.7449	$265.74	$265.75	$265.70
Purchase #5	$114.37	5.339%	$120.4762	$120.48	$120.50	$120.50
Purchase #6	$160.30	5.293%	$168.7847	$168.78	$168.80	$168.80
Purchase #7	$117.43	10.538%	$129.8048	$129.80	$129.80	$129.80
7 purchase totals =	$1,074.60		$1,145.4263	$1,145.42	$1,145.45	$1,145.40