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	$155.59	6.528%	$165.7469	$165.75	$165.75	$165.70
Purchase #2	$82.71	7.659%	$89.0448	$89.04	$89.05	$89.00
Purchase #3	$47.79	12.175%	$53.6084	$53.61	$53.60	$53.60
Purchase #4	$37.58	13.475%	$42.6439	$42.64	$42.65	$42.60
Purchase #5	$200.66	4.313%	$209.3145	$209.31	$209.30	$209.30
Purchase #6	$167.87	5.293%	$176.7554	$176.76	$176.75	$176.80
Purchase #7	$23.26	4.311%	$24.2627	$24.26	$24.25	$24.30
7 purchase totals =	$715.46		$761.3766	$761.37	$761.35	$761.30