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	$231.85	10.388%	$255.9346	$255.93	$255.95	$255.90
Purchase #2	$177.86	12.604%	$200.2775	$200.28	$200.30	$200.30
Purchase #3	$107.58	7.112%	$115.2311	$115.23	$115.25	$115.20
Purchase #4	$199.82	7.380%	$214.5667	$214.57	$214.55	$214.60
Purchase #5	$215.73	7.430%	$231.7587	$231.76	$231.75	$231.80
Purchase #6	$54.46	9.116%	$59.4246	$59.42	$59.40	$59.40
Purchase #7	$98.39	12.652%	$110.8383	$110.84	$110.85	$110.80
7 purchase totals =	$1,085.69		$1,188.0315	$1,188.03	$1,188.05	$1,188.00