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	$156.28	6.507%	$166.4491	$166.45	$166.45	$166.40
Purchase #2	$117.29	5.605%	$123.8641	$123.86	$123.85	$123.90
Purchase #3	$234.40	4.497%	$244.941	$244.94	$244.95	$244.90
Purchase #4	$158.30	6.299%	$168.2713	$168.27	$168.25	$168.30
Purchase #5	$27.44	7.232%	$29.4245	$29.42	$29.40	$29.40
Purchase #6	$213.33	3.869%	$221.5837	$221.58	$221.60	$221.60
Purchase #7	$102.41	10.768%	$113.4375	$113.44	$113.45	$113.40
7 purchase totals =	$1,009.45		$1,067.9712	$1,067.96	$1,067.95	$1,067.90