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	$108.59	11.383%	$120.9508	$120.95	$120.95	$121.00
Purchase #2	$188.56	11.236%	$209.7466	$209.75	$209.75	$209.70
Purchase #3	$138.28	11.770%	$154.5556	$154.56	$154.55	$154.60
Purchase #4	$75.52	13.737%	$85.8942	$85.89	$85.90	$85.90
Purchase #5	$62.93	6.253%	$66.865	$66.87	$66.85	$66.90
Purchase #6	$105.89	5.517%	$111.732	$111.73	$111.75	$111.70
Purchase #7	$24.76	7.572%	$26.6348	$26.63	$26.65	$26.60
7 purchase totals =	$704.53		$776.3790	$776.38	$776.40	$776.40