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	$93.67	12.361%	$105.2485	$105.25	$105.25	$105.20
Purchase #2	$18.71	11.351%	$20.8338	$20.83	$20.85	$20.80
Purchase #3	$88.89	11.365%	$98.9923	$98.99	$99.00	$99.00
Purchase #4	$213.34	13.261%	$241.631	$241.63	$241.65	$241.60
Purchase #5	$226.85	3.158%	$234.0139	$234.01	$234.00	$234.00
Purchase #6	$22.69	12.807%	$25.5959	$25.60	$25.60	$25.60
Purchase #7	$239.78	6.352%	$255.0108	$255.01	$255.00	$255.00
7 purchase totals =	$903.93		$981.3262	$981.32	$981.35	$981.20