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	$22.62	8.782%	$24.6065	$24.61	$24.60	$24.60
Purchase #2	$97.97	12.118%	$109.842	$109.84	$109.85	$109.80
Purchase #3	$180.58	8.673%	$196.2417	$196.24	$196.25	$196.20
Purchase #4	$247.88	12.744%	$279.4698	$279.47	$279.45	$279.50
Purchase #5	$106.36	5.645%	$112.364	$112.36	$112.35	$112.40
Purchase #6	$28.41	10.477%	$31.3865	$31.39	$31.40	$31.40
Purchase #7	$237.63	10.611%	$262.8449	$262.84	$262.85	$262.80
7 purchase totals =	$921.45		$1,016.7554	$1,016.75	$1,016.75	$1,016.70