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	$209.77	3.705%	$217.542	$217.54	$217.55	$217.50
Purchase #2	$78.69	3.637%	$81.552	$81.55	$81.55	$81.60
Purchase #3	$215.69	10.397%	$238.1153	$238.12	$238.10	$238.10
Purchase #4	$96.54	5.107%	$101.4703	$101.47	$101.45	$101.50
Purchase #5	$111.96	4.224%	$116.6892	$116.69	$116.70	$116.70
Purchase #6	$58.42	12.148%	$65.5169	$65.52	$65.50	$65.50
Purchase #7	$158.79	10.363%	$175.2454	$175.25	$175.25	$175.20
7 purchase totals =	$929.86		$996.1311	$996.14	$996.10	$996.10