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	$34.69	11.813%	$38.7879	$38.79	$38.80	$38.80
Purchase #2	$189.54	3.503%	$196.1796	$196.18	$196.20	$196.20
Purchase #3	$217.56	4.720%	$227.8288	$227.83	$227.85	$227.80
Purchase #4	$167.72	10.381%	$185.131	$185.13	$185.15	$185.10
Purchase #5	$115.99	7.779%	$125.0129	$125.01	$125.00	$125.00
Purchase #6	$132.79	11.863%	$148.5429	$148.54	$148.55	$148.50
Purchase #7	$192.44	9.422%	$210.5717	$210.57	$210.55	$210.60
7 purchase totals =	$1,050.73		$1,132.0548	$1,132.05	$1,132.10	$1,132.00