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	$51.44	3.542%	$53.262	$53.26	$53.25	$53.30
Purchase #2	$173.86	9.422%	$190.2411	$190.24	$190.25	$190.20
Purchase #3	$85.69	5.756%	$90.6223	$90.62	$90.60	$90.60
Purchase #4	$245.67	3.480%	$254.2193	$254.22	$254.20	$254.20
Purchase #5	$102.27	13.568%	$116.146	$116.15	$116.15	$116.10
Purchase #6	$90.62	5.835%	$95.9077	$95.91	$95.90	$95.90
Purchase #7	$228.34	13.767%	$259.7756	$259.78	$259.80	$259.80
7 purchase totals =	$977.89		$1,060.1740	$1,060.18	$1,060.15	$1,060.10