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	$63.87	7.237%	$68.4923	$68.49	$68.50	$68.50
Purchase #2	$57.27	13.713%	$65.1234	$65.12	$65.10	$65.10
Purchase #3	$182.41	7.787%	$196.6143	$196.61	$196.60	$196.60
Purchase #4	$237.91	5.236%	$250.367	$250.37	$250.35	$250.40
Purchase #5	$215.56	11.156%	$239.6079	$239.61	$239.60	$239.60
Purchase #6	$132.53	4.116%	$137.9849	$137.98	$138.00	$138.00
Purchase #7	$172.38	11.623%	$192.4157	$192.42	$192.40	$192.40
7 purchase totals =	$1,061.93		$1,150.6055	$1,150.60	$1,150.55	$1,150.60