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	$237.89	9.608%	$260.7465	$260.75	$260.75	$260.70
Purchase #2	$99.83	12.558%	$112.3667	$112.37	$112.35	$112.40
Purchase #3	$175.40	3.412%	$181.3846	$181.38	$181.40	$181.40
Purchase #4	$99.48	4.212%	$103.6701	$103.67	$103.65	$103.70
Purchase #5	$78.52	4.808%	$82.2952	$82.30	$82.30	$82.30
Purchase #6	$213.73	8.460%	$231.8116	$231.81	$231.80	$231.80
Purchase #7	$84.32	10.175%	$92.8996	$92.90	$92.90	$92.90
7 purchase totals =	$989.17		$1,065.1743	$1,065.18	$1,065.15	$1,065.20