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	$87.81	9.616%	$96.2538	$96.25	$96.25	$96.30
Purchase #2	$135.61	13.474%	$153.8821	$153.88	$153.90	$153.90
Purchase #3	$123.43	11.372%	$137.4665	$137.47	$137.45	$137.50
Purchase #4	$241.95	10.434%	$267.1951	$267.20	$267.20	$267.20
Purchase #5	$66.88	7.444%	$71.8585	$71.86	$71.85	$71.90
Purchase #6	$68.99	13.240%	$78.1243	$78.12	$78.10	$78.10
Purchase #7	$143.86	4.466%	$150.2848	$150.28	$150.30	$150.30
7 purchase totals =	$868.53		$955.0651	$955.06	$955.05	$955.20