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	$48.37	10.420%	$53.4102	$53.41	$53.40	$53.40
Purchase #2	$182.90	13.403%	$207.4141	$207.41	$207.40	$207.40
Purchase #3	$99.37	4.290%	$103.633	$103.63	$103.65	$103.60
Purchase #4	$140.48	13.495%	$159.4378	$159.44	$159.45	$159.40
Purchase #5	$54.45	9.311%	$59.5198	$59.52	$59.50	$59.50
Purchase #6	$134.65	4.472%	$140.6715	$140.67	$140.65	$140.70
Purchase #7	$134.25	12.136%	$150.5426	$150.54	$150.55	$150.50
7 purchase totals =	$794.47		$874.6290	$874.62	$874.60	$874.50