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	$141.90	4.142%	$147.7775	$147.78	$147.80	$147.80
Purchase #2	$93.79	7.258%	$100.5973	$100.60	$100.60	$100.60
Purchase #3	$48.79	10.455%	$53.891	$53.89	$53.90	$53.90
Purchase #4	$98.41	6.176%	$104.4878	$104.49	$104.50	$104.50
Purchase #5	$40.86	5.343%	$43.0431	$43.04	$43.05	$43.00
Purchase #6	$74.31	8.105%	$80.3328	$80.33	$80.35	$80.30
Purchase #7	$183.38	6.489%	$195.2795	$195.28	$195.30	$195.30
7 purchase totals =	$681.44		$725.4090	$725.41	$725.50	$725.40