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	$163.98	9.169%	$179.0153	$179.02	$179.00	$179.00
Purchase #2	$59.43	3.233%	$61.3514	$61.35	$61.35	$61.40
Purchase #3	$185.96	12.700%	$209.5769	$209.58	$209.60	$209.60
Purchase #4	$39.38	7.359%	$42.278	$42.28	$42.30	$42.30
Purchase #5	$245.67	5.131%	$258.2753	$258.28	$258.30	$258.30
Purchase #6	$9.52	10.848%	$10.5527	$10.55	$10.55	$10.60
Purchase #7	$224.69	11.714%	$251.0102	$251.01	$251.00	$251.00
7 purchase totals =	$928.63		$1,012.0598	$1,012.07	$1,012.10	$1,012.20