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	$181.27	8.458%	$196.6018	$196.60	$196.60	$196.60
Purchase #2	$140.64	5.307%	$148.1038	$148.10	$148.10	$148.10
Purchase #3	$156.61	9.137%	$170.9195	$170.92	$170.90	$170.90
Purchase #4	$212.44	4.519%	$222.0402	$222.04	$222.05	$222.00
Purchase #5	$109.53	11.337%	$121.9474	$121.95	$121.95	$121.90
Purchase #6	$168.47	9.469%	$184.4224	$184.42	$184.40	$184.40
Purchase #7	$140.73	11.170%	$156.4495	$156.45	$156.45	$156.40
7 purchase totals =	$1,109.69		$1,200.4846	$1,200.48	$1,200.45	$1,200.30