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	$86.27	5.332%	$90.8699	$90.87	$90.85	$90.90
Purchase #2	$55.46	3.126%	$57.1937	$57.19	$57.20	$57.20
Purchase #3	$117.67	11.794%	$131.548	$131.55	$131.55	$131.50
Purchase #4	$135.32	11.771%	$151.2485	$151.25	$151.25	$151.20
Purchase #5	$62.94	3.472%	$65.1253	$65.13	$65.15	$65.10
Purchase #6	$160.98	8.626%	$174.8661	$174.87	$174.85	$174.90
Purchase #7	$117.94	4.287%	$122.9961	$123.00	$123.00	$123.00
7 purchase totals =	$736.58		$793.8476	$793.86	$793.85	$793.80