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	$153.99	3.804%	$159.8478	$159.85	$159.85	$159.80
Purchase #2	$122.91	13.306%	$139.2644	$139.26	$139.25	$139.30
Purchase #3	$74.27	5.850%	$78.6148	$78.61	$78.60	$78.60
Purchase #4	$171.51	13.741%	$195.0772	$195.08	$195.10	$195.10
Purchase #5	$49.46	8.315%	$53.5726	$53.57	$53.55	$53.60
Purchase #6	$50.27	5.194%	$52.881	$52.88	$52.90	$52.90
Purchase #7	$93.53	12.165%	$104.9079	$104.91	$104.90	$104.90
7 purchase totals =	$715.94		$784.1657	$784.16	$784.15	$784.20