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	$65.65	13.171%	$74.2968	$74.30	$74.30	$74.30
Purchase #2	$243.83	7.383%	$261.832	$261.83	$261.85	$261.80
Purchase #3	$232.27	10.528%	$256.7234	$256.72	$256.70	$256.70
Purchase #4	$142.31	11.378%	$158.502	$158.50	$158.50	$158.50
Purchase #5	$139.83	9.214%	$152.7139	$152.71	$152.70	$152.70
Purchase #6	$78.47	9.702%	$86.0832	$86.08	$86.10	$86.10
Purchase #7	$166.47	5.363%	$175.3978	$175.40	$175.40	$175.40
7 purchase totals =	$1,068.83		$1,165.5491	$1,165.54	$1,165.55	$1,165.50