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	$162.47	3.693%	$168.47	$168.47	$168.45	$168.50
Purchase #2	$15.76	8.374%	$17.0797	$17.08	$17.10	$17.10
Purchase #3	$168.33	7.777%	$181.421	$181.42	$181.40	$181.40
Purchase #4	$171.75	5.404%	$181.0314	$181.03	$181.05	$181.00
Purchase #5	$50.87	11.680%	$56.8116	$56.81	$56.80	$56.80
Purchase #6	$248.53	3.276%	$256.6718	$256.67	$256.65	$256.70
Purchase #7	$74.82	4.277%	$78.0201	$78.02	$78.00	$78.00
7 purchase totals =	$892.53		$939.5056	$939.50	$939.45	$939.50