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	$64.62	10.697%	$71.5324	$71.53	$71.55	$71.50
Purchase #2	$153.40	12.241%	$172.1777	$172.18	$172.20	$172.20
Purchase #3	$167.25	10.598%	$184.9752	$184.98	$185.00	$185.00
Purchase #4	$125.62	13.767%	$142.9141	$142.91	$142.90	$142.90
Purchase #5	$109.29	6.757%	$116.6747	$116.67	$116.65	$116.70
Purchase #6	$136.30	7.854%	$147.005	$147.01	$147.00	$147.00
Purchase #7	$132.58	5.323%	$139.6372	$139.64	$139.65	$139.60
7 purchase totals =	$889.06		$974.9163	$974.92	$974.95	$974.90