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	$120.42	10.128%	$132.6161	$132.62	$132.60	$132.60
Purchase #2	$200.97	10.321%	$221.7121	$221.71	$221.70	$221.70
Purchase #3	$249.46	7.131%	$267.249	$267.25	$267.25	$267.20
Purchase #4	$39.45	5.233%	$41.5144	$41.51	$41.50	$41.50
Purchase #5	$49.69	7.387%	$53.3606	$53.36	$53.35	$53.40
Purchase #6	$242.90	9.224%	$265.3051	$265.31	$265.30	$265.30
Purchase #7	$131.48	10.658%	$145.4931	$145.49	$145.50	$145.50
7 purchase totals =	$1,034.37		$1,127.2504	$1,127.25	$1,127.20	$1,127.20