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	$113.33	13.679%	$128.8324	$128.83	$128.85	$128.80
Purchase #2	$24.38	6.864%	$26.0534	$26.05	$26.05	$26.10
Purchase #3	$181.78	3.357%	$187.8824	$187.88	$187.90	$187.90
Purchase #4	$160.76	5.454%	$169.5279	$169.53	$169.55	$169.50
Purchase #5	$70.87	11.208%	$78.8131	$78.81	$78.80	$78.80
Purchase #6	$102.55	8.634%	$111.4042	$111.40	$111.40	$111.40
Purchase #7	$159.47	7.804%	$171.915	$171.92	$171.90	$171.90
7 purchase totals =	$813.14		$874.4284	$874.42	$874.45	$874.40