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	$109.85	8.487%	$119.173	$119.17	$119.15	$119.20
Purchase #2	$54.58	6.582%	$58.1725	$58.17	$58.15	$58.20
Purchase #3	$122.33	11.510%	$136.4102	$136.41	$136.40	$136.40
Purchase #4	$88.43	3.416%	$91.4508	$91.45	$91.45	$91.50
Purchase #5	$22.91	6.354%	$24.3657	$24.37	$24.35	$24.40
Purchase #6	$95.43	5.653%	$100.8247	$100.82	$100.80	$100.80
Purchase #7	$162.30	11.197%	$180.4727	$180.47	$180.45	$180.50
7 purchase totals =	$655.83		$710.8696	$710.86	$710.75	$711.00