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	$103.38	12.480%	$116.2818	$116.28	$116.30	$116.30
Purchase #2	$113.86	8.564%	$123.611	$123.61	$123.60	$123.60
Purchase #3	$113.43	4.668%	$118.7249	$118.72	$118.70	$118.70
Purchase #4	$144.93	4.558%	$151.5359	$151.54	$151.55	$151.50
Purchase #5	$109.58	11.807%	$122.5181	$122.52	$122.50	$122.50
Purchase #6	$156.90	13.844%	$178.6212	$178.62	$178.60	$178.60
Purchase #7	$231.50	8.572%	$251.3442	$251.34	$251.35	$251.30
7 purchase totals =	$973.58		$1,062.6371	$1,062.63	$1,062.60	$1,062.50