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	$156.93	3.228%	$161.9957	$162.00	$162.00	$162.00
Purchase #2	$142.92	7.714%	$153.9448	$153.94	$153.95	$153.90
Purchase #3	$202.73	5.821%	$214.5309	$214.53	$214.55	$214.50
Purchase #4	$138.83	8.699%	$150.9068	$150.91	$150.90	$150.90
Purchase #5	$169.49	5.809%	$179.3357	$179.34	$179.35	$179.30
Purchase #6	$103.94	9.136%	$113.436	$113.44	$113.45	$113.40
Purchase #7	$40.31	13.653%	$45.8135	$45.81	$45.80	$45.80
7 purchase totals =	$955.15		$1,019.9634	$1,019.97	$1,020.00	$1,019.80