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	$109.80	4.136%	$114.3413	$114.34	$114.35	$114.30
Purchase #2	$15.91	5.728%	$16.8213	$16.82	$16.80	$16.80
Purchase #3	$178.91	5.611%	$188.9486	$188.95	$188.95	$188.90
Purchase #4	$233.57	4.701%	$244.5501	$244.55	$244.55	$244.60
Purchase #5	$95.39	5.504%	$100.6403	$100.64	$100.65	$100.60
Purchase #6	$20.25	6.252%	$21.516	$21.52	$21.50	$21.50
Purchase #7	$106.49	6.423%	$113.3299	$113.33	$113.35	$113.30
7 purchase totals =	$760.32		$800.1475	$800.15	$800.15	$800.00