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	$71.34	5.540%	$75.2922	$75.29	$75.30	$75.30
Purchase #2	$146.25	7.693%	$157.501	$157.50	$157.50	$157.50
Purchase #3	$17.87	11.780%	$19.9751	$19.98	$20.00	$20.00
Purchase #4	$54.45	13.697%	$61.908	$61.91	$61.90	$61.90
Purchase #5	$184.31	6.831%	$196.9002	$196.90	$196.90	$196.90
Purchase #6	$150.64	13.854%	$171.5097	$171.51	$171.50	$171.50
Purchase #7	$100.34	13.185%	$113.5698	$113.57	$113.55	$113.60
7 purchase totals =	$725.20		$796.6560	$796.66	$796.65	$796.70