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	$213.33	11.640%	$238.1616	$238.16	$238.15	$238.20
Purchase #2	$150.55	11.570%	$167.9686	$167.97	$167.95	$168.00
Purchase #3	$83.26	10.423%	$91.9382	$91.94	$91.95	$91.90
Purchase #4	$191.59	5.847%	$202.7923	$202.79	$202.80	$202.80
Purchase #5	$164.33	4.761%	$172.1538	$172.15	$172.15	$172.20
Purchase #6	$101.54	12.867%	$114.6052	$114.61	$114.60	$114.60
Purchase #7	$42.79	4.773%	$44.8324	$44.83	$44.85	$44.80
7 purchase totals =	$947.39		$1,032.4521	$1,032.45	$1,032.45	$1,032.50