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	$104.59	9.168%	$114.1788	$114.18	$114.20	$114.20
Purchase #2	$140.60	13.746%	$159.9269	$159.93	$159.95	$159.90
Purchase #3	$29.39	6.813%	$31.3923	$31.39	$31.40	$31.40
Purchase #4	$66.47	10.290%	$73.3098	$73.31	$73.30	$73.30
Purchase #5	$144.94	4.801%	$151.8986	$151.90	$151.90	$151.90
Purchase #6	$135.26	11.495%	$150.8081	$150.81	$150.80	$150.80
Purchase #7	$171.66	13.778%	$195.3113	$195.31	$195.30	$195.30
7 purchase totals =	$792.91		$876.8258	$876.83	$876.85	$876.80