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	$94.46	13.772%	$107.469	$107.47	$107.45	$107.50
Purchase #2	$188.59	11.604%	$210.474	$210.47	$210.45	$210.50
Purchase #3	$60.74	7.164%	$65.0914	$65.09	$65.10	$65.10
Purchase #4	$167.56	10.319%	$184.8505	$184.85	$184.85	$184.90
Purchase #5	$11.85	10.501%	$13.0944	$13.09	$13.10	$13.10
Purchase #6	$67.48	7.484%	$72.5302	$72.53	$72.55	$72.50
Purchase #7	$118.82	6.638%	$126.7073	$126.71	$126.70	$126.70
7 purchase totals =	$709.50		$780.2168	$780.21	$780.20	$780.30