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	$6.83	6.355%	$7.264	$7.26	$7.25	$7.30
Purchase #2	$47.46	11.264%	$52.8059	$52.81	$52.80	$52.80
Purchase #3	$226.31	12.296%	$254.1371	$254.14	$254.15	$254.10
Purchase #4	$146.42	3.869%	$152.085	$152.09	$152.10	$152.10
Purchase #5	$170.94	10.225%	$188.4186	$188.42	$188.40	$188.40
Purchase #6	$78.82	9.569%	$86.3623	$86.36	$86.35	$86.40
Purchase #7	$236.82	4.813%	$248.2181	$248.22	$248.20	$248.20
7 purchase totals =	$913.60		$989.2910	$989.30	$989.25	$989.30