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	$241.84	11.546%	$269.7628	$269.76	$269.75	$269.80
Purchase #2	$250.50	12.504%	$281.8225	$281.82	$281.80	$281.80
Purchase #3	$202.96	5.116%	$213.3434	$213.34	$213.35	$213.30
Purchase #4	$199.77	7.352%	$214.4571	$214.46	$214.45	$214.50
Purchase #5	$66.95	8.263%	$72.4821	$72.48	$72.50	$72.50
Purchase #6	$101.55	11.350%	$113.0759	$113.08	$113.10	$113.10
Purchase #7	$103.59	12.475%	$116.5129	$116.51	$116.50	$116.50
7 purchase totals =	$1,167.16		$1,281.4567	$1,281.45	$1,281.45	$1,281.50