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	$133.88	8.183%	$144.8354	$144.84	$144.85	$144.80
Purchase #2	$242.33	7.148%	$259.6517	$259.65	$259.65	$259.70
Purchase #3	$78.78	4.246%	$82.125	$82.13	$82.15	$82.10
Purchase #4	$50.88	7.467%	$54.6792	$54.68	$54.70	$54.70
Purchase #5	$56.70	9.647%	$62.1698	$62.17	$62.15	$62.20
Purchase #6	$109.87	13.506%	$124.709	$124.71	$124.70	$124.70
Purchase #7	$224.81	11.144%	$249.8628	$249.86	$249.85	$249.90
7 purchase totals =	$897.25		$978.0329	$978.04	$978.05	$978.10