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	$64.27	5.267%	$67.6551	$67.66	$67.65	$67.70
Purchase #2	$164.34	12.427%	$184.7625	$184.76	$184.75	$184.80
Purchase #3	$243.42	5.348%	$256.4381	$256.44	$256.45	$256.40
Purchase #4	$78.26	5.860%	$82.846	$82.85	$82.85	$82.80
Purchase #5	$53.80	10.354%	$59.3705	$59.37	$59.35	$59.40
Purchase #6	$153.61	9.569%	$168.3089	$168.31	$168.30	$168.30
Purchase #7	$248.59	12.815%	$280.4468	$280.45	$280.45	$280.40
7 purchase totals =	$1,006.29		$1,099.8279	$1,099.84	$1,099.80	$1,099.80