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	$176.28	6.247%	$187.2922	$187.29	$187.30	$187.30
Purchase #2	$22.58	5.609%	$23.8465	$23.85	$23.85	$23.80
Purchase #3	$28.51	11.700%	$31.8457	$31.85	$31.85	$31.80
Purchase #4	$80.48	13.626%	$91.4462	$91.45	$91.45	$91.40
Purchase #5	$193.52	3.171%	$199.6565	$199.66	$199.65	$199.70
Purchase #6	$119.28	7.824%	$128.6125	$128.61	$128.60	$128.60
Purchase #7	$108.81	13.473%	$123.47	$123.47	$123.45	$123.50
7 purchase totals =	$729.46		$786.1696	$786.18	$786.15	$786.10