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	$83.33	9.634%	$91.358	$91.36	$91.35	$91.40
Purchase #2	$108.93	13.225%	$123.336	$123.34	$123.35	$123.30
Purchase #3	$125.81	8.401%	$136.3793	$136.38	$136.40	$136.40
Purchase #4	$180.47	5.226%	$189.9014	$189.90	$189.90	$189.90
Purchase #5	$104.72	6.138%	$111.1477	$111.15	$111.15	$111.10
Purchase #6	$141.43	8.496%	$153.4459	$153.45	$153.45	$153.40
Purchase #7	$109.35	12.484%	$123.0013	$123.00	$123.00	$123.00
7 purchase totals =	$854.04		$928.5696	$928.58	$928.60	$928.50