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	$191.38	13.566%	$217.3426	$217.34	$217.35	$217.30
Purchase #2	$53.39	11.641%	$59.6051	$59.61	$59.60	$59.60
Purchase #3	$90.58	9.386%	$99.0818	$99.08	$99.10	$99.10
Purchase #4	$117.49	3.343%	$121.4177	$121.42	$121.40	$121.40
Purchase #5	$143.29	11.175%	$159.3027	$159.30	$159.30	$159.30
Purchase #6	$109.70	6.557%	$116.893	$116.89	$116.90	$116.90
Purchase #7	$151.92	11.498%	$169.3878	$169.39	$169.40	$169.40
7 purchase totals =	$857.75		$943.0307	$943.03	$943.05	$943.00