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	$199.44	10.623%	$220.6265	$220.63	$220.65	$220.60
Purchase #2	$48.68	3.124%	$50.2008	$50.20	$50.20	$50.20
Purchase #3	$221.79	10.233%	$244.4858	$244.49	$244.50	$244.50
Purchase #4	$163.65	5.223%	$172.1974	$172.20	$172.20	$172.20
Purchase #5	$209.77	3.381%	$216.8623	$216.86	$216.85	$216.90
Purchase #6	$199.90	11.500%	$222.8885	$222.89	$222.90	$222.90
Purchase #7	$80.66	10.847%	$89.4092	$89.41	$89.40	$89.40
7 purchase totals =	$1,123.89		$1,216.6705	$1,216.68	$1,216.70	$1,216.70