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	$214.37	6.175%	$227.6073	$227.61	$227.60	$227.60
Purchase #2	$40.96	13.683%	$46.5646	$46.56	$46.55	$46.60
Purchase #3	$86.59	4.671%	$90.6346	$90.63	$90.65	$90.60
Purchase #4	$80.64	7.556%	$86.7332	$86.73	$86.75	$86.70
Purchase #5	$219.72	3.279%	$226.9246	$226.92	$226.90	$226.90
Purchase #6	$152.26	12.534%	$171.3443	$171.34	$171.35	$171.30
Purchase #7	$164.26	9.244%	$179.4442	$179.44	$179.45	$179.40
7 purchase totals =	$958.80		$1,029.2528	$1,029.23	$1,029.25	$1,029.10