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	$191.62	12.691%	$215.9385	$215.94	$215.95	$215.90
Purchase #2	$244.38	12.745%	$275.5262	$275.53	$275.55	$275.50
Purchase #3	$89.88	3.313%	$92.8577	$92.86	$92.85	$92.90
Purchase #4	$54.49	9.649%	$59.7477	$59.75	$59.75	$59.70
Purchase #5	$87.45	11.639%	$97.6283	$97.63	$97.65	$97.60
Purchase #6	$15.64	13.556%	$17.7602	$17.76	$17.75	$17.80
Purchase #7	$207.30	7.511%	$222.8703	$222.87	$222.85	$222.90
7 purchase totals =	$890.76		$982.3289	$982.34	$982.35	$982.30