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	$132.50	11.716%	$148.0237	$148.02	$148.00	$148.00
Purchase #2	$28.82	9.155%	$31.4585	$31.46	$31.45	$31.50
Purchase #3	$175.32	5.690%	$185.2957	$185.30	$185.30	$185.30
Purchase #4	$166.53	3.829%	$172.9064	$172.91	$172.90	$172.90
Purchase #5	$94.69	9.631%	$103.8096	$103.81	$103.80	$103.80
Purchase #6	$234.82	4.781%	$246.0467	$246.05	$246.05	$246.00
Purchase #7	$172.77	10.814%	$191.4533	$191.45	$191.45	$191.50
7 purchase totals =	$1,005.45		$1,078.9939	$1,079.00	$1,078.95	$1,079.00