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	$48.63	7.749%	$52.3983	$52.40	$52.40	$52.40
Purchase #2	$194.32	3.149%	$200.4391	$200.44	$200.45	$200.40
Purchase #3	$164.64	4.341%	$171.787	$171.79	$171.80	$171.80
Purchase #4	$136.42	4.224%	$142.1824	$142.18	$142.20	$142.20
Purchase #5	$207.43	11.470%	$231.2222	$231.22	$231.20	$231.20
Purchase #6	$15.54	11.866%	$17.384	$17.38	$17.40	$17.40
Purchase #7	$197.91	3.832%	$205.4939	$205.49	$205.50	$205.50
7 purchase totals =	$964.89		$1,020.9069	$1,020.90	$1,020.95	$1,020.90