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	$150.26	8.358%	$162.8187	$162.82	$162.80	$162.80
Purchase #2	$221.56	13.838%	$252.2195	$252.22	$252.20	$252.20
Purchase #3	$54.88	3.154%	$56.6109	$56.61	$56.60	$56.60
Purchase #4	$123.96	8.449%	$134.4334	$134.43	$134.45	$134.40
Purchase #5	$72.48	8.291%	$78.4893	$78.49	$78.50	$78.50
Purchase #6	$133.89	10.831%	$148.3916	$148.39	$148.40	$148.40
Purchase #7	$79.38	11.699%	$88.6667	$88.67	$88.65	$88.70
7 purchase totals =	$836.41		$921.6301	$921.63	$921.60	$921.60