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	$106.53	6.417%	$113.366	$113.37	$113.35	$113.40
Purchase #2	$55.64	12.498%	$62.5939	$62.59	$62.60	$62.60
Purchase #3	$17.59	5.136%	$18.4934	$18.49	$18.50	$18.50
Purchase #4	$231.47	10.451%	$255.6609	$255.66	$255.65	$255.70
Purchase #5	$57.53	12.301%	$64.6068	$64.61	$64.60	$64.60
Purchase #6	$162.40	5.822%	$171.8549	$171.85	$171.85	$171.90
Purchase #7	$198.28	6.769%	$211.7016	$211.70	$211.70	$211.70
7 purchase totals =	$829.44		$898.2775	$898.27	$898.25	$898.40