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	$41.88	11.833%	$46.8357	$46.84	$46.85	$46.80
Purchase #2	$176.80	5.365%	$186.2853	$186.29	$186.30	$186.30
Purchase #3	$241.43	13.436%	$273.8685	$273.87	$273.85	$273.90
Purchase #4	$173.38	13.385%	$196.5869	$196.59	$196.60	$196.60
Purchase #5	$175.45	6.162%	$186.2612	$186.26	$186.25	$186.30
Purchase #6	$29.29	3.510%	$30.3181	$30.32	$30.30	$30.30
Purchase #7	$206.61	11.611%	$230.5995	$230.60	$230.60	$230.60
7 purchase totals =	$1,044.84		$1,150.7552	$1,150.77	$1,150.75	$1,150.80