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	$183.33	5.205%	$192.8723	$192.87	$192.85	$192.90
Purchase #2	$241.94	8.679%	$262.938	$262.94	$262.95	$262.90
Purchase #3	$143.69	4.784%	$150.5641	$150.56	$150.55	$150.60
Purchase #4	$95.59	6.324%	$101.6351	$101.64	$101.65	$101.60
Purchase #5	$168.58	13.238%	$190.8966	$190.90	$190.90	$190.90
Purchase #6	$224.77	9.273%	$245.6129	$245.61	$245.60	$245.60
Purchase #7	$134.99	6.538%	$143.8156	$143.82	$143.80	$143.80
7 purchase totals =	$1,192.89		$1,288.3346	$1,288.34	$1,288.30	$1,288.30