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	$179.44	4.637%	$187.7606	$187.76	$187.75	$187.80
Purchase #2	$71.59	13.827%	$81.4887	$81.49	$81.50	$81.50
Purchase #3	$167.56	5.835%	$177.3371	$177.34	$177.35	$177.30
Purchase #4	$143.76	6.179%	$152.6429	$152.64	$152.65	$152.60
Purchase #5	$126.84	5.823%	$134.2259	$134.23	$134.25	$134.20
Purchase #6	$57.90	3.348%	$59.8385	$59.84	$59.85	$59.80
Purchase #7	$137.89	11.342%	$153.5295	$153.53	$153.55	$153.50
7 purchase totals =	$884.98		$946.8232	$946.83	$946.90	$946.70