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	$131.85	8.727%	$143.3565	$143.36	$143.35	$143.40
Purchase #2	$183.92	3.105%	$189.6307	$189.63	$189.65	$189.60
Purchase #3	$250.35	3.714%	$259.648	$259.65	$259.65	$259.60
Purchase #4	$159.74	8.822%	$173.8323	$173.83	$173.85	$173.80
Purchase #5	$49.77	9.681%	$54.5882	$54.59	$54.60	$54.60
Purchase #6	$27.99	12.622%	$31.5229	$31.52	$31.50	$31.50
Purchase #7	$109.91	12.568%	$123.7235	$123.72	$123.70	$123.70
7 purchase totals =	$913.53		$976.3021	$976.30	$976.30	$976.20