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	$56.27	8.167%	$60.8656	$60.87	$60.85	$60.90
Purchase #2	$122.35	5.117%	$128.6106	$128.61	$128.60	$128.60
Purchase #3	$144.80	11.835%	$161.9371	$161.94	$161.95	$161.90
Purchase #4	$213.48	5.663%	$225.5694	$225.57	$225.55	$225.60
Purchase #5	$123.87	6.513%	$131.9377	$131.94	$131.95	$131.90
Purchase #6	$179.80	4.263%	$187.4649	$187.46	$187.45	$187.50
Purchase #7	$174.75	12.305%	$196.253	$196.25	$196.25	$196.30
7 purchase totals =	$1,015.32		$1,092.6383	$1,092.64	$1,092.60	$1,092.70