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	$221.65	7.611%	$238.5198	$238.52	$238.50	$238.50
Purchase #2	$153.34	6.357%	$163.0878	$163.09	$163.10	$163.10
Purchase #3	$238.90	3.802%	$247.983	$247.98	$248.00	$248.00
Purchase #4	$132.53	7.411%	$142.3518	$142.35	$142.35	$142.40
Purchase #5	$74.94	5.187%	$78.8271	$78.83	$78.85	$78.80
Purchase #6	$64.67	10.511%	$71.4675	$71.47	$71.45	$71.50
Purchase #7	$247.90	6.636%	$264.3506	$264.35	$264.35	$264.40
7 purchase totals =	$1,133.93		$1,206.5876	$1,206.59	$1,206.60	$1,206.70