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	$116.71	9.277%	$127.5372	$127.54	$127.55	$127.50
Purchase #2	$44.47	11.446%	$49.56	$49.56	$49.55	$49.60
Purchase #3	$119.81	8.151%	$129.5757	$129.58	$129.60	$129.60
Purchase #4	$182.83	13.641%	$207.7698	$207.77	$207.75	$207.80
Purchase #5	$70.32	11.603%	$78.4792	$78.48	$78.50	$78.50
Purchase #6	$53.76	7.559%	$57.8237	$57.82	$57.80	$57.80
Purchase #7	$211.34	9.606%	$231.6413	$231.64	$231.65	$231.60
7 purchase totals =	$799.24		$882.3869	$882.39	$882.40	$882.40