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	$121.80	4.770%	$127.6099	$127.61	$127.60	$127.60
Purchase #2	$96.38	7.154%	$103.275	$103.28	$103.30	$103.30
Purchase #3	$212.62	11.646%	$237.3817	$237.38	$237.40	$237.40
Purchase #4	$148.67	6.438%	$158.2414	$158.24	$158.25	$158.20
Purchase #5	$187.28	4.701%	$196.084	$196.08	$196.10	$196.10
Purchase #6	$110.62	10.380%	$122.1024	$122.10	$122.10	$122.10
Purchase #7	$37.87	7.145%	$40.5758	$40.58	$40.60	$40.60
7 purchase totals =	$915.24		$985.2702	$985.27	$985.35	$985.30