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	$222.63	9.294%	$243.3212	$243.32	$243.30	$243.30
Purchase #2	$231.84	8.114%	$250.6515	$250.65	$250.65	$250.70
Purchase #3	$130.47	7.354%	$140.0648	$140.06	$140.05	$140.10
Purchase #4	$76.63	11.693%	$85.5903	$85.59	$85.60	$85.60
Purchase #5	$64.52	13.138%	$72.9966	$73.00	$73.00	$73.00
Purchase #6	$131.54	8.762%	$143.0655	$143.07	$143.05	$143.10
Purchase #7	$124.51	12.360%	$139.8994	$139.90	$139.90	$139.90
7 purchase totals =	$982.14		$1,075.5893	$1,075.59	$1,075.55	$1,075.70