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	$197.33	12.748%	$222.4856	$222.49	$222.50	$222.50
Purchase #2	$57.39	7.250%	$61.5508	$61.55	$61.55	$61.60
Purchase #3	$126.98	7.709%	$136.7689	$136.77	$136.75	$136.80
Purchase #4	$182.57	10.329%	$201.4277	$201.43	$201.45	$201.40
Purchase #5	$147.66	12.748%	$166.4837	$166.48	$166.50	$166.50
Purchase #6	$164.85	3.250%	$170.2076	$170.21	$170.20	$170.20
Purchase #7	$208.69	6.595%	$222.4531	$222.45	$222.45	$222.50
7 purchase totals =	$1,085.47		$1,181.3774	$1,181.38	$1,181.40	$1,181.50