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	$168.70	3.835%	$175.1696	$175.17	$175.15	$175.20
Purchase #2	$124.52	5.781%	$131.7185	$131.72	$131.70	$131.70
Purchase #3	$118.34	13.587%	$134.4189	$134.42	$134.40	$134.40
Purchase #4	$92.84	7.295%	$99.6127	$99.61	$99.60	$99.60
Purchase #5	$196.94	10.414%	$217.4493	$217.45	$217.45	$217.40
Purchase #6	$141.86	10.393%	$156.6035	$156.60	$156.60	$156.60
Purchase #7	$6.82	10.390%	$7.5286	$7.53	$7.55	$7.50
7 purchase totals =	$850.02		$922.5011	$922.50	$922.45	$922.40