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	$38.72	11.295%	$43.0934	$43.09	$43.10	$43.10
Purchase #2	$203.29	8.772%	$221.1226	$221.12	$221.10	$221.10
Purchase #3	$41.64	8.639%	$45.2373	$45.24	$45.25	$45.20
Purchase #4	$246.96	7.633%	$265.8105	$265.81	$265.80	$265.80
Purchase #5	$227.29	12.384%	$255.4376	$255.44	$255.45	$255.40
Purchase #6	$180.55	3.544%	$186.9487	$186.95	$186.95	$186.90
Purchase #7	$136.25	3.392%	$140.8716	$140.87	$140.85	$140.90
7 purchase totals =	$1,074.70		$1,158.5217	$1,158.52	$1,158.50	$1,158.40