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	$96.60	9.572%	$105.8466	$105.85	$105.85	$105.80
Purchase #2	$198.27	7.697%	$213.5308	$213.53	$213.55	$213.50
Purchase #3	$118.41	4.111%	$123.2778	$123.28	$123.30	$123.30
Purchase #4	$163.85	4.785%	$171.6902	$171.69	$171.70	$171.70
Purchase #5	$24.61	11.295%	$27.3897	$27.39	$27.40	$27.40
Purchase #6	$204.79	6.276%	$217.6426	$217.64	$217.65	$217.60
Purchase #7	$203.69	11.503%	$227.1205	$227.12	$227.10	$227.10
7 purchase totals =	$1,010.22		$1,086.4982	$1,086.50	$1,086.55	$1,086.40