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	$247.89	4.790%	$259.7639	$259.76	$259.75	$259.80
Purchase #2	$58.63	12.598%	$66.0162	$66.02	$66.00	$66.00
Purchase #3	$40.64	11.787%	$45.4302	$45.43	$45.45	$45.40
Purchase #4	$176.39	13.874%	$200.8623	$200.86	$200.85	$200.90
Purchase #5	$233.99	9.601%	$256.4554	$256.46	$256.45	$256.50
Purchase #6	$75.68	12.153%	$84.8774	$84.88	$84.90	$84.90
Purchase #7	$166.40	8.475%	$180.5024	$180.50	$180.50	$180.50
7 purchase totals =	$999.62		$1,093.9078	$1,093.91	$1,093.90	$1,094.00