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	$240.60	4.165%	$250.621	$250.62	$250.60	$250.60
Purchase #2	$182.54	5.768%	$193.0689	$193.07	$193.05	$193.10
Purchase #3	$154.95	7.796%	$167.0299	$167.03	$167.05	$167.00
Purchase #4	$113.34	12.680%	$127.7115	$127.71	$127.70	$127.70
Purchase #5	$157.97	10.559%	$174.6501	$174.65	$174.65	$174.70
Purchase #6	$213.47	5.473%	$225.1532	$225.15	$225.15	$225.20
Purchase #7	$84.65	7.409%	$90.9217	$90.92	$90.90	$90.90
7 purchase totals =	$1,147.52		$1,229.1563	$1,229.15	$1,229.10	$1,229.20