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	$231.49	12.169%	$259.66	$259.66	$259.65	$259.70
Purchase #2	$89.76	6.436%	$95.537	$95.54	$95.55	$95.50
Purchase #3	$142.82	12.383%	$160.5054	$160.51	$160.50	$160.50
Purchase #4	$150.39	8.319%	$162.9009	$162.90	$162.90	$162.90
Purchase #5	$105.34	9.455%	$115.2999	$115.30	$115.30	$115.30
Purchase #6	$82.75	11.720%	$92.4483	$92.45	$92.45	$92.40
Purchase #7	$165.73	4.189%	$172.6724	$172.67	$172.65	$172.70
7 purchase totals =	$968.28		$1,059.0239	$1,059.03	$1,059.00	$1,059.00