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	$85.65	13.789%	$97.4603	$97.46	$97.45	$97.50
Purchase #2	$17.26	4.421%	$18.0231	$18.02	$18.00	$18.00
Purchase #3	$201.76	10.231%	$222.4021	$222.40	$222.40	$222.40
Purchase #4	$16.84	10.102%	$18.5412	$18.54	$18.55	$18.50
Purchase #5	$144.70	7.760%	$155.9287	$155.93	$155.95	$155.90
Purchase #6	$20.40	13.730%	$23.2009	$23.20	$23.20	$23.20
Purchase #7	$115.81	13.666%	$131.6366	$131.64	$131.65	$131.60
7 purchase totals =	$602.42		$667.1929	$667.19	$667.20	$667.10