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	$149.52	13.313%	$169.4256	$169.43	$169.45	$169.40
Purchase #2	$82.72	3.280%	$85.4332	$85.43	$85.45	$85.40
Purchase #3	$52.54	4.731%	$55.0257	$55.03	$55.05	$55.00
Purchase #4	$12.78	5.705%	$13.5091	$13.51	$13.50	$13.50
Purchase #5	$124.34	11.207%	$138.2748	$138.27	$138.25	$138.30
Purchase #6	$109.95	4.470%	$114.8648	$114.86	$114.85	$114.90
Purchase #7	$170.67	5.774%	$180.5245	$180.52	$180.50	$180.50
7 purchase totals =	$702.52		$757.0577	$757.05	$757.05	$757.00