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	$239.54	13.789%	$272.5702	$272.57	$272.55	$272.60
Purchase #2	$18.76	12.301%	$21.0677	$21.07	$21.05	$21.10
Purchase #3	$79.82	6.638%	$85.1185	$85.12	$85.10	$85.10
Purchase #4	$175.76	3.113%	$181.2314	$181.23	$181.25	$181.20
Purchase #5	$186.63	5.484%	$196.8648	$196.86	$196.85	$196.90
Purchase #6	$123.58	6.228%	$131.2766	$131.28	$131.30	$131.30
Purchase #7	$129.81	3.638%	$134.5325	$134.53	$134.55	$134.50
7 purchase totals =	$953.90		$1,022.6617	$1,022.66	$1,022.65	$1,022.70