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	$232.91	5.832%	$246.4933	$246.49	$246.50	$246.50
Purchase #2	$155.37	4.600%	$162.517	$162.52	$162.50	$162.50
Purchase #3	$227.98	6.464%	$242.7166	$242.72	$242.70	$242.70
Purchase #4	$181.41	13.419%	$205.7534	$205.75	$205.75	$205.80
Purchase #5	$29.26	10.721%	$32.397	$32.40	$32.40	$32.40
Purchase #6	$76.38	11.777%	$85.3753	$85.38	$85.40	$85.40
Purchase #7	$155.69	8.124%	$168.3383	$168.34	$168.35	$168.30
7 purchase totals =	$1,059.00		$1,143.5909	$1,143.60	$1,143.60	$1,143.60