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	$183.27	3.177%	$189.0925	$189.09	$189.10	$189.10
Purchase #2	$38.35	9.165%	$41.8648	$41.86	$41.85	$41.90
Purchase #3	$203.77	8.721%	$221.5408	$221.54	$221.55	$221.50
Purchase #4	$223.60	3.714%	$231.9045	$231.90	$231.90	$231.90
Purchase #5	$51.53	7.620%	$55.4566	$55.46	$55.45	$55.50
Purchase #6	$140.87	4.632%	$147.3951	$147.40	$147.40	$147.40
Purchase #7	$206.36	5.650%	$218.0193	$218.02	$218.00	$218.00
7 purchase totals =	$1,047.75		$1,105.2736	$1,105.27	$1,105.25	$1,105.30