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	$194.40	13.128%	$219.9208	$219.92	$219.90	$219.90
Purchase #2	$10.61	5.385%	$11.1813	$11.18	$11.20	$11.20
Purchase #3	$41.33	5.797%	$43.7259	$43.73	$43.75	$43.70
Purchase #4	$114.65	4.468%	$119.7726	$119.77	$119.75	$119.80
Purchase #5	$203.44	7.386%	$218.4661	$218.47	$218.45	$218.50
Purchase #6	$92.87	9.391%	$101.5914	$101.59	$101.60	$101.60
Purchase #7	$72.83	12.669%	$82.0568	$82.06	$82.05	$82.10
7 purchase totals =	$730.13		$796.7149	$796.72	$796.70	$796.80