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	$93.47	10.342%	$103.1367	$103.14	$103.15	$103.10
Purchase #2	$88.67	4.763%	$92.8934	$92.89	$92.90	$92.90
Purchase #3	$117.85	13.615%	$133.8953	$133.90	$133.90	$133.90
Purchase #4	$223.90	5.632%	$236.51	$236.51	$236.50	$236.50
Purchase #5	$89.96	11.258%	$100.0877	$100.09	$100.10	$100.10
Purchase #6	$73.54	4.610%	$76.9302	$76.93	$76.95	$76.90
Purchase #7	$19.42	3.356%	$20.0717	$20.07	$20.05	$20.10
7 purchase totals =	$706.81		$763.5250	$763.53	$763.55	$763.50