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	$168.93	9.666%	$185.2588	$185.26	$185.25	$185.30
Purchase #2	$243.27	4.852%	$255.0735	$255.07	$255.05	$255.10
Purchase #3	$91.75	12.387%	$103.1151	$103.12	$103.10	$103.10
Purchase #4	$238.25	11.718%	$266.1681	$266.17	$266.15	$266.20
Purchase #5	$90.79	3.555%	$94.0176	$94.02	$94.00	$94.00
Purchase #6	$148.54	12.172%	$166.6203	$166.62	$166.60	$166.60
Purchase #7	$199.39	7.267%	$213.8797	$213.88	$213.90	$213.90
7 purchase totals =	$1,180.92		$1,284.1331	$1,284.14	$1,284.05	$1,284.20