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	$42.79	3.134%	$44.131	$44.13	$44.15	$44.10
Purchase #2	$74.30	10.565%	$82.1498	$82.15	$82.15	$82.10
Purchase #3	$187.34	9.593%	$205.3115	$205.31	$205.30	$205.30
Purchase #4	$196.89	5.578%	$207.8725	$207.87	$207.85	$207.90
Purchase #5	$233.33	12.745%	$263.0679	$263.07	$263.05	$263.10
Purchase #6	$165.33	9.278%	$180.6693	$180.67	$180.65	$180.70
Purchase #7	$114.63	12.177%	$128.5885	$128.59	$128.60	$128.60
7 purchase totals =	$1,014.61		$1,111.7905	$1,111.79	$1,111.75	$1,111.80