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	$169.50	12.601%	$190.8587	$190.86	$190.85	$190.90
Purchase #2	$47.91	9.193%	$52.3144	$52.31	$52.30	$52.30
Purchase #3	$198.45	3.362%	$205.1219	$205.12	$205.10	$205.10
Purchase #4	$99.33	4.484%	$103.784	$103.78	$103.80	$103.80
Purchase #5	$111.71	9.336%	$122.1392	$122.14	$122.15	$122.10
Purchase #6	$79.85	4.858%	$83.7291	$83.73	$83.75	$83.70
Purchase #7	$55.26	7.823%	$59.583	$59.58	$59.60	$59.60
7 purchase totals =	$762.01		$817.5303	$817.52	$817.55	$817.50