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	$208.86	3.632%	$216.4458	$216.45	$216.45	$216.40
Purchase #2	$91.97	8.755%	$100.022	$100.02	$100.00	$100.00
Purchase #3	$50.74	9.125%	$55.37	$55.37	$55.35	$55.40
Purchase #4	$87.61	8.613%	$95.1558	$95.16	$95.15	$95.20
Purchase #5	$246.84	13.651%	$280.5361	$280.54	$280.55	$280.50
Purchase #6	$68.36	6.722%	$72.9552	$72.96	$72.95	$73.00
Purchase #7	$114.43	3.360%	$118.2748	$118.27	$118.25	$118.30
7 purchase totals =	$868.81		$938.7597	$938.77	$938.70	$938.80