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	$200.52	8.436%	$217.4359	$217.44	$217.45	$217.40
Purchase #2	$162.85	13.308%	$184.5221	$184.52	$184.50	$184.50
Purchase #3	$206.74	11.751%	$231.034	$231.03	$231.05	$231.00
Purchase #4	$84.61	6.769%	$90.3373	$90.34	$90.35	$90.30
Purchase #5	$8.66	10.128%	$9.5371	$9.54	$9.55	$9.50
Purchase #6	$182.39	7.868%	$196.7404	$196.74	$196.75	$196.70
Purchase #7	$148.86	10.300%	$164.1926	$164.19	$164.20	$164.20
7 purchase totals =	$994.63		$1,093.7994	$1,093.80	$1,093.85	$1,093.60