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	$232.70	3.468%	$240.77	$240.77	$240.75	$240.80
Purchase #2	$218.97	11.611%	$244.3946	$244.39	$244.40	$244.40
Purchase #3	$48.52	10.459%	$53.5947	$53.59	$53.60	$53.60
Purchase #4	$173.46	3.238%	$179.0766	$179.08	$179.10	$179.10
Purchase #5	$189.88	9.782%	$208.4541	$208.45	$208.45	$208.50
Purchase #6	$104.49	12.337%	$117.3809	$117.38	$117.40	$117.40
Purchase #7	$74.33	11.158%	$82.6237	$82.62	$82.60	$82.60
7 purchase totals =	$1,042.35		$1,126.2946	$1,126.28	$1,126.30	$1,126.40