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	$61.71	11.849%	$69.022	$69.02	$69.00	$69.00
Purchase #2	$44.44	7.141%	$47.6135	$47.61	$47.60	$47.60
Purchase #3	$247.72	13.470%	$281.0879	$281.09	$281.10	$281.10
Purchase #4	$55.34	7.109%	$59.2741	$59.27	$59.25	$59.30
Purchase #5	$137.47	7.826%	$148.2284	$148.23	$148.25	$148.20
Purchase #6	$42.89	9.148%	$46.8136	$46.81	$46.80	$46.80
Purchase #7	$34.84	11.654%	$38.9003	$38.90	$38.90	$38.90
7 purchase totals =	$624.41		$690.9398	$690.93	$690.90	$690.90