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	$117.42	12.138%	$131.6724	$131.67	$131.65	$131.70
Purchase #2	$104.53	8.377%	$113.2865	$113.29	$113.30	$113.30
Purchase #3	$110.60	3.337%	$114.2907	$114.29	$114.30	$114.30
Purchase #4	$51.85	11.114%	$57.6126	$57.61	$57.60	$57.60
Purchase #5	$155.72	7.738%	$167.7696	$167.77	$167.75	$167.80
Purchase #6	$9.27	10.121%	$10.2082	$10.21	$10.20	$10.20
Purchase #7	$18.97	8.599%	$20.6012	$20.60	$20.60	$20.60
7 purchase totals =	$568.36		$615.4412	$615.44	$615.40	$615.50