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	$126.31	13.151%	$142.921	$142.92	$142.90	$142.90
Purchase #2	$17.88	13.240%	$20.2473	$20.25	$20.25	$20.20
Purchase #3	$106.87	5.321%	$112.5566	$112.56	$112.55	$112.60
Purchase #4	$64.42	4.676%	$67.4323	$67.43	$67.45	$67.40
Purchase #5	$88.74	10.317%	$97.8953	$97.90	$97.90	$97.90
Purchase #6	$196.43	6.605%	$209.4042	$209.40	$209.40	$209.40
Purchase #7	$206.68	10.351%	$228.0734	$228.07	$228.05	$228.10
7 purchase totals =	$807.33		$878.5301	$878.53	$878.50	$878.50