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	$186.28	5.347%	$196.2404	$196.24	$196.25	$196.20
Purchase #2	$111.73	4.789%	$117.0807	$117.08	$117.10	$117.10
Purchase #3	$233.72	8.491%	$253.5652	$253.57	$253.55	$253.60
Purchase #4	$148.59	11.312%	$165.3985	$165.40	$165.40	$165.40
Purchase #5	$169.80	12.503%	$191.0301	$191.03	$191.05	$191.00
Purchase #6	$63.55	3.469%	$65.7545	$65.75	$65.75	$65.80
Purchase #7	$247.25	11.246%	$275.0557	$275.06	$275.05	$275.10
7 purchase totals =	$1,160.92		$1,264.1251	$1,264.13	$1,264.15	$1,264.20