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	$19.58	5.251%	$20.6081	$20.61	$20.60	$20.60
Purchase #2	$226.59	3.471%	$234.4549	$234.45	$234.45	$234.50
Purchase #3	$143.53	5.578%	$151.5361	$151.54	$151.55	$151.50
Purchase #4	$200.45	13.552%	$227.615	$227.62	$227.60	$227.60
Purchase #5	$152.92	12.578%	$172.1543	$172.15	$172.15	$172.20
Purchase #6	$123.66	13.394%	$140.223	$140.22	$140.20	$140.20
Purchase #7	$172.79	4.393%	$180.3807	$180.38	$180.40	$180.40
7 purchase totals =	$1,039.52		$1,126.9721	$1,126.97	$1,126.95	$1,127.00