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	$81.26	5.700%	$85.8918	$85.89	$85.90	$85.90
Purchase #2	$226.96	5.510%	$239.4655	$239.47	$239.45	$239.50
Purchase #3	$28.35	11.805%	$31.6967	$31.70	$31.70	$31.70
Purchase #4	$243.99	5.276%	$256.8629	$256.86	$256.85	$256.90
Purchase #5	$65.33	11.223%	$72.662	$72.66	$72.65	$72.70
Purchase #6	$40.97	6.690%	$43.7109	$43.71	$43.70	$43.70
Purchase #7	$107.55	5.519%	$113.4857	$113.49	$113.50	$113.50
7 purchase totals =	$794.41		$843.7755	$843.78	$843.75	$843.90