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	$246.92	8.247%	$267.2835	$267.28	$267.30	$267.30
Purchase #2	$198.39	13.520%	$225.2123	$225.21	$225.20	$225.20
Purchase #3	$77.76	7.343%	$83.4699	$83.47	$83.45	$83.50
Purchase #4	$244.39	6.597%	$260.5124	$260.51	$260.50	$260.50
Purchase #5	$154.36	13.121%	$174.6136	$174.61	$174.60	$174.60
Purchase #6	$65.36	4.809%	$68.5032	$68.50	$68.50	$68.50
Purchase #7	$78.89	5.120%	$82.9292	$82.93	$82.95	$82.90
7 purchase totals =	$1,066.07		$1,162.5241	$1,162.51	$1,162.50	$1,162.50