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	$40.58	8.103%	$43.8682	$43.87	$43.85	$43.90
Purchase #2	$155.42	6.200%	$165.056	$165.06	$165.05	$165.10
Purchase #3	$7.32	3.684%	$7.5897	$7.59	$7.60	$7.60
Purchase #4	$153.46	4.219%	$159.9345	$159.93	$159.95	$159.90
Purchase #5	$148.89	10.155%	$164.0098	$164.01	$164.00	$164.00
Purchase #6	$159.64	13.295%	$180.8641	$180.86	$180.85	$180.90
Purchase #7	$12.69	7.392%	$13.628	$13.63	$13.65	$13.60
7 purchase totals =	$678.00		$734.9503	$734.95	$734.95	$735.00