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	$197.28	6.622%	$210.3439	$210.34	$210.35	$210.30
Purchase #2	$192.92	4.105%	$200.8394	$200.84	$200.85	$200.80
Purchase #3	$122.63	4.868%	$128.5996	$128.60	$128.60	$128.60
Purchase #4	$221.76	7.198%	$237.7223	$237.72	$237.70	$237.70
Purchase #5	$171.78	5.298%	$180.8809	$180.88	$180.90	$180.90
Purchase #6	$48.95	3.568%	$50.6965	$50.70	$50.70	$50.70
Purchase #7	$65.64	10.399%	$72.4659	$72.47	$72.45	$72.50
7 purchase totals =	$1,020.96		$1,081.5485	$1,081.55	$1,081.55	$1,081.50