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	$54.66	11.637%	$61.0208	$61.02	$61.00	$61.00
Purchase #2	$140.77	3.495%	$145.6899	$145.69	$145.70	$145.70
Purchase #3	$19.36	10.581%	$21.4085	$21.41	$21.40	$21.40
Purchase #4	$109.63	3.305%	$113.2533	$113.25	$113.25	$113.30
Purchase #5	$197.84	12.466%	$222.5027	$222.50	$222.50	$222.50
Purchase #6	$22.81	12.260%	$25.6065	$25.61	$25.60	$25.60
Purchase #7	$112.66	13.171%	$127.4984	$127.50	$127.50	$127.50
7 purchase totals =	$657.73		$716.9801	$716.98	$716.95	$717.00