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	$186.34	4.266%	$194.2893	$194.29	$194.30	$194.30
Purchase #2	$221.74	8.585%	$240.7764	$240.78	$240.80	$240.80
Purchase #3	$244.73	12.620%	$275.6149	$275.61	$275.60	$275.60
Purchase #4	$144.70	7.443%	$155.47	$155.47	$155.45	$155.50
Purchase #5	$170.80	8.536%	$185.3795	$185.38	$185.40	$185.40
Purchase #6	$111.32	11.154%	$123.7366	$123.74	$123.75	$123.70
Purchase #7	$104.78	5.725%	$110.7787	$110.78	$110.80	$110.80
7 purchase totals =	$1,184.41		$1,286.0454	$1,286.05	$1,286.10	$1,286.10