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	$200.31	9.758%	$219.8562	$219.86	$219.85	$219.90
Purchase #2	$29.34	7.258%	$31.4695	$31.47	$31.45	$31.50
Purchase #3	$88.25	12.275%	$99.0827	$99.08	$99.10	$99.10
Purchase #4	$136.77	11.653%	$152.7078	$152.71	$152.70	$152.70
Purchase #5	$20.28	6.786%	$21.6562	$21.66	$21.65	$21.70
Purchase #6	$80.46	13.732%	$91.5088	$91.51	$91.50	$91.50
Purchase #7	$63.55	10.137%	$69.9921	$69.99	$70.00	$70.00
7 purchase totals =	$618.96		$686.2733	$686.28	$686.25	$686.40