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	$51.86	5.162%	$54.537	$54.54	$54.55	$54.50
Purchase #2	$168.59	10.808%	$186.8112	$186.81	$186.80	$186.80
Purchase #3	$249.41	10.477%	$275.5407	$275.54	$275.55	$275.50
Purchase #4	$100.50	5.144%	$105.6697	$105.67	$105.65	$105.70
Purchase #5	$199.81	3.354%	$206.5116	$206.51	$206.50	$206.50
Purchase #6	$133.63	12.742%	$150.6571	$150.66	$150.65	$150.70
Purchase #7	$61.62	3.438%	$63.7385	$63.74	$63.75	$63.70
7 purchase totals =	$965.42		$1,043.4658	$1,043.47	$1,043.45	$1,043.40