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	$104.89	3.790%	$108.8653	$108.87	$108.85	$108.90
Purchase #2	$216.89	4.667%	$227.0123	$227.01	$227.00	$227.00
Purchase #3	$139.54	3.177%	$143.9732	$143.97	$143.95	$144.00
Purchase #4	$91.68	13.186%	$103.7689	$103.77	$103.75	$103.80
Purchase #5	$180.53	13.215%	$204.387	$204.39	$204.40	$204.40
Purchase #6	$185.56	13.621%	$210.8351	$210.84	$210.85	$210.80
Purchase #7	$18.91	11.110%	$21.0109	$21.01	$21.00	$21.00
7 purchase totals =	$938.00		$1,019.8527	$1,019.86	$1,019.80	$1,019.90