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	$131.72	10.428%	$145.4558	$145.46	$145.45	$145.50
Purchase #2	$137.89	10.660%	$152.5891	$152.59	$152.60	$152.60
Purchase #3	$102.67	6.545%	$109.3898	$109.39	$109.40	$109.40
Purchase #4	$171.51	3.375%	$177.2985	$177.30	$177.30	$177.30
Purchase #5	$224.72	9.319%	$245.6617	$245.66	$245.65	$245.70
Purchase #6	$89.26	7.185%	$95.6733	$95.67	$95.65	$95.70
Purchase #7	$238.25	13.131%	$269.5346	$269.53	$269.55	$269.50
7 purchase totals =	$1,096.02		$1,195.6028	$1,195.60	$1,195.60	$1,195.70