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	$100.37	5.706%	$106.0971	$106.10	$106.10	$106.10
Purchase #2	$231.68	5.249%	$243.8409	$243.84	$243.85	$243.80
Purchase #3	$45.67	13.224%	$51.7094	$51.71	$51.70	$51.70
Purchase #4	$233.57	7.257%	$250.5202	$250.52	$250.50	$250.50
Purchase #5	$28.60	13.671%	$32.5099	$32.51	$32.50	$32.50
Purchase #6	$220.88	10.314%	$243.6616	$243.66	$243.65	$243.70
Purchase #7	$76.87	4.753%	$80.5236	$80.52	$80.50	$80.50
7 purchase totals =	$937.64		$1,008.8627	$1,008.86	$1,008.80	$1,008.80