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	$235.51	12.439%	$264.8051	$264.81	$264.80	$264.80
Purchase #2	$81.52	7.709%	$87.8044	$87.80	$87.80	$87.80
Purchase #3	$187.62	11.177%	$208.5903	$208.59	$208.60	$208.60
Purchase #4	$75.67	13.376%	$85.7916	$85.79	$85.80	$85.80
Purchase #5	$40.59	5.524%	$42.8322	$42.83	$42.85	$42.80
Purchase #6	$215.40	5.163%	$226.5211	$226.52	$226.50	$226.50
Purchase #7	$145.61	13.579%	$165.3824	$165.38	$165.40	$165.40
7 purchase totals =	$981.92		$1,081.7271	$1,081.72	$1,081.75	$1,081.70