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	$239.69	10.389%	$264.5914	$264.59	$264.60	$264.60
Purchase #2	$36.73	3.252%	$37.9245	$37.92	$37.90	$37.90
Purchase #3	$238.60	10.423%	$263.4693	$263.47	$263.45	$263.50
Purchase #4	$62.72	13.745%	$71.3409	$71.34	$71.35	$71.30
Purchase #5	$180.90	13.713%	$205.7068	$205.71	$205.70	$205.70
Purchase #6	$136.26	10.629%	$150.7431	$150.74	$150.75	$150.70
Purchase #7	$85.93	5.822%	$90.9328	$90.93	$90.95	$90.90
7 purchase totals =	$980.83		$1,084.7088	$1,084.70	$1,084.70	$1,084.60