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	$164.60	11.790%	$184.0063	$184.01	$184.00	$184.00
Purchase #2	$54.90	4.389%	$57.3096	$57.31	$57.30	$57.30
Purchase #3	$23.85	13.316%	$27.0259	$27.03	$27.05	$27.00
Purchase #4	$153.34	10.551%	$169.5189	$169.52	$169.50	$169.50
Purchase #5	$24.33	12.202%	$27.2987	$27.30	$27.30	$27.30
Purchase #6	$162.35	6.247%	$172.492	$172.49	$172.50	$172.50
Purchase #7	$58.89	8.443%	$63.8621	$63.86	$63.85	$63.90
7 purchase totals =	$642.26		$701.5135	$701.52	$701.50	$701.50