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	$114.50	13.676%	$130.159	$130.16	$130.15	$130.20
Purchase #2	$150.77	11.629%	$168.303	$168.30	$168.30	$168.30
Purchase #3	$226.44	7.487%	$243.3936	$243.39	$243.40	$243.40
Purchase #4	$64.84	9.741%	$71.1561	$71.16	$71.15	$71.20
Purchase #5	$155.63	5.809%	$164.6705	$164.67	$164.65	$164.70
Purchase #6	$128.87	4.161%	$134.2323	$134.23	$134.25	$134.20
Purchase #7	$19.54	11.451%	$21.7775	$21.78	$21.80	$21.80
7 purchase totals =	$860.59		$933.6920	$933.69	$933.70	$933.80