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	$43.97	6.157%	$46.6772	$46.68	$46.70	$46.70
Purchase #2	$39.82	5.112%	$41.8556	$41.86	$41.85	$41.90
Purchase #3	$138.83	8.358%	$150.4334	$150.43	$150.45	$150.40
Purchase #4	$246.70	3.236%	$254.6832	$254.68	$254.70	$254.70
Purchase #5	$153.57	11.703%	$171.5423	$171.54	$171.55	$171.50
Purchase #6	$139.86	8.320%	$151.4964	$151.50	$151.50	$151.50
Purchase #7	$153.82	7.620%	$165.5411	$165.54	$165.55	$165.50
7 purchase totals =	$916.57		$982.2292	$982.23	$982.30	$982.20