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	$99.26	13.434%	$112.5946	$112.59	$112.60	$112.60
Purchase #2	$151.96	10.653%	$168.1483	$168.15	$168.15	$168.10
Purchase #3	$5.62	5.834%	$5.9479	$5.95	$5.95	$5.90
Purchase #4	$70.38	11.314%	$78.3428	$78.34	$78.35	$78.30
Purchase #5	$178.29	10.382%	$196.8001	$196.80	$196.80	$196.80
Purchase #6	$119.42	5.395%	$125.8627	$125.86	$125.85	$125.90
Purchase #7	$5.96	4.434%	$6.2243	$6.22	$6.20	$6.20
7 purchase totals =	$630.89		$693.9207	$693.91	$693.90	$693.80