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	$20.38	7.632%	$21.9354	$21.94	$21.95	$21.90
Purchase #2	$73.61	12.722%	$82.9747	$82.97	$82.95	$83.00
Purchase #3	$101.32	8.457%	$109.8886	$109.89	$109.90	$109.90
Purchase #4	$119.68	6.801%	$127.8194	$127.82	$127.80	$127.80
Purchase #5	$111.88	8.205%	$121.0598	$121.06	$121.05	$121.10
Purchase #6	$192.64	8.615%	$209.2359	$209.24	$209.25	$209.20
Purchase #7	$168.53	6.409%	$179.3311	$179.33	$179.35	$179.30
7 purchase totals =	$788.04		$852.2449	$852.25	$852.25	$852.20