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	$97.84	10.155%	$107.7757	$107.78	$107.80	$107.80
Purchase #2	$239.93	4.525%	$250.7868	$250.79	$250.80	$250.80
Purchase #3	$78.66	13.737%	$89.4655	$89.47	$89.45	$89.50
Purchase #4	$244.27	5.145%	$256.8377	$256.84	$256.85	$256.80
Purchase #5	$66.34	6.722%	$70.7994	$70.80	$70.80	$70.80
Purchase #6	$99.47	13.494%	$112.8925	$112.89	$112.90	$112.90
Purchase #7	$85.29	10.167%	$93.9614	$93.96	$93.95	$94.00
7 purchase totals =	$911.80		$982.5190	$982.53	$982.55	$982.60