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	$139.52	9.238%	$152.4089	$152.41	$152.40	$152.40
Purchase #2	$83.39	8.862%	$90.78	$90.78	$90.80	$90.80
Purchase #3	$125.90	13.324%	$142.6749	$142.67	$142.65	$142.70
Purchase #4	$55.69	4.102%	$57.9744	$57.97	$57.95	$58.00
Purchase #5	$163.30	7.868%	$176.1484	$176.15	$176.15	$176.10
Purchase #6	$187.92	4.419%	$196.2242	$196.22	$196.20	$196.20
Purchase #7	$5.55	9.268%	$6.0644	$6.06	$6.05	$6.10
7 purchase totals =	$761.27		$822.2752	$822.26	$822.20	$822.30