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	$208.33	12.138%	$233.6171	$233.62	$233.60	$233.60
Purchase #2	$15.62	9.130%	$17.0461	$17.05	$17.05	$17.00
Purchase #3	$222.63	7.266%	$238.8063	$238.81	$238.80	$238.80
Purchase #4	$189.43	4.849%	$198.6155	$198.62	$198.60	$198.60
Purchase #5	$66.39	7.208%	$71.1754	$71.18	$71.20	$71.20
Purchase #6	$155.50	11.805%	$173.8568	$173.86	$173.85	$173.90
Purchase #7	$67.83	7.326%	$72.7992	$72.80	$72.80	$72.80
7 purchase totals =	$925.73		$1,005.9164	$1,005.94	$1,005.90	$1,005.90