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	$100.29	5.328%	$105.6335	$105.63	$105.65	$105.60
Purchase #2	$86.31	4.582%	$90.2647	$90.26	$90.25	$90.30
Purchase #3	$182.98	7.500%	$196.7035	$196.70	$196.70	$196.70
Purchase #4	$225.26	9.516%	$246.6957	$246.70	$246.70	$246.70
Purchase #5	$44.66	8.711%	$48.5503	$48.55	$48.55	$48.60
Purchase #6	$130.48	10.669%	$144.4009	$144.40	$144.40	$144.40
Purchase #7	$122.91	8.498%	$133.3549	$133.35	$133.35	$133.40
7 purchase totals =	$892.89		$965.6035	$965.59	$965.60	$965.70