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	$73.88	6.228%	$78.4812	$78.48	$78.50	$78.50
Purchase #2	$143.43	6.470%	$152.7099	$152.71	$152.70	$152.70
Purchase #3	$218.97	7.337%	$235.0358	$235.04	$235.05	$235.00
Purchase #4	$81.86	6.440%	$87.1318	$87.13	$87.15	$87.10
Purchase #5	$228.54	5.845%	$241.8982	$241.90	$241.90	$241.90
Purchase #6	$220.54	6.210%	$234.2355	$234.24	$234.25	$234.20
Purchase #7	$64.31	10.478%	$71.0484	$71.05	$71.05	$71.00
7 purchase totals =	$1,031.53		$1,100.5408	$1,100.55	$1,100.60	$1,100.40