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	$63.40	11.687%	$70.8096	$70.81	$70.80	$70.80
Purchase #2	$206.32	10.411%	$227.8	$227.80	$227.80	$227.80
Purchase #3	$169.25	7.775%	$182.4092	$182.41	$182.40	$182.40
Purchase #4	$151.31	10.811%	$167.6681	$167.67	$167.65	$167.70
Purchase #5	$150.54	11.668%	$168.105	$168.11	$168.10	$168.10
Purchase #6	$103.65	4.780%	$108.6045	$108.60	$108.60	$108.60
Purchase #7	$71.31	11.575%	$79.5641	$79.56	$79.55	$79.60
7 purchase totals =	$915.78		$1,004.9605	$1,004.96	$1,004.90	$1,005.00