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	$178.69	11.378%	$199.0213	$199.02	$199.00	$199.00
Purchase #2	$124.42	3.151%	$128.3405	$128.34	$128.35	$128.30
Purchase #3	$72.93	12.296%	$81.8975	$81.90	$81.90	$81.90
Purchase #4	$126.38	11.195%	$140.5282	$140.53	$140.55	$140.50
Purchase #5	$129.31	10.545%	$142.9457	$142.95	$142.95	$142.90
Purchase #6	$101.67	3.534%	$105.263	$105.26	$105.25	$105.30
Purchase #7	$67.46	7.804%	$72.7246	$72.72	$72.70	$72.70
7 purchase totals =	$800.86		$870.7208	$870.72	$870.70	$870.60