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	$89.76	13.497%	$101.8749	$101.87	$101.85	$101.90
Purchase #2	$219.26	4.261%	$228.6027	$228.60	$228.60	$228.60
Purchase #3	$217.97	11.715%	$243.5052	$243.51	$243.50	$243.50
Purchase #4	$137.27	10.736%	$152.0073	$152.01	$152.00	$152.00
Purchase #5	$111.81	9.854%	$122.8278	$122.83	$122.85	$122.80
Purchase #6	$178.60	7.681%	$192.3183	$192.32	$192.30	$192.30
Purchase #7	$135.96	6.158%	$144.3324	$144.33	$144.35	$144.30
7 purchase totals =	$1,090.63		$1,185.4686	$1,185.47	$1,185.45	$1,185.40