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	$180.46	10.746%	$199.8522	$199.85	$199.85	$199.90
Purchase #2	$158.98	8.454%	$172.4202	$172.42	$172.40	$172.40
Purchase #3	$147.86	12.855%	$166.8674	$166.87	$166.85	$166.90
Purchase #4	$130.37	8.111%	$140.9443	$140.94	$140.95	$140.90
Purchase #5	$237.80	4.871%	$249.3832	$249.38	$249.40	$249.40
Purchase #6	$90.39	13.646%	$102.7246	$102.72	$102.70	$102.70
Purchase #7	$87.32	10.481%	$96.472	$96.47	$96.45	$96.50
7 purchase totals =	$1,033.18		$1,128.6639	$1,128.65	$1,128.60	$1,128.70