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	$112.56	6.201%	$119.5398	$119.54	$119.55	$119.50
Purchase #2	$6.90	4.776%	$7.2295	$7.23	$7.25	$7.20
Purchase #3	$32.55	5.640%	$34.3858	$34.39	$34.40	$34.40
Purchase #4	$214.92	4.150%	$223.8392	$223.84	$223.85	$223.80
Purchase #5	$73.54	3.808%	$76.3404	$76.34	$76.35	$76.30
Purchase #6	$41.76	7.791%	$45.0135	$45.01	$45.00	$45.00
Purchase #7	$49.53	10.223%	$54.5935	$54.59	$54.60	$54.60
7 purchase totals =	$531.76		$560.9417	$560.94	$561.00	$560.80