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	$217.69	12.469%	$244.8338	$244.83	$244.85	$244.80
Purchase #2	$49.69	4.632%	$51.9916	$51.99	$52.00	$52.00
Purchase #3	$142.67	9.318%	$155.964	$155.96	$155.95	$156.00
Purchase #4	$56.78	4.380%	$59.267	$59.27	$59.25	$59.30
Purchase #5	$121.42	13.597%	$137.9295	$137.93	$137.95	$137.90
Purchase #6	$30.42	6.588%	$32.4241	$32.42	$32.40	$32.40
Purchase #7	$85.37	4.685%	$89.3696	$89.37	$89.35	$89.40
7 purchase totals =	$704.04		$771.7796	$771.77	$771.75	$771.80