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	$222.96	6.771%	$238.0566	$238.06	$238.05	$238.10
Purchase #2	$230.50	12.446%	$259.188	$259.19	$259.20	$259.20
Purchase #3	$35.27	7.434%	$37.892	$37.89	$37.90	$37.90
Purchase #4	$23.72	9.192%	$25.9003	$25.90	$25.90	$25.90
Purchase #5	$108.66	9.463%	$118.9425	$118.94	$118.95	$118.90
Purchase #6	$86.93	3.196%	$89.7083	$89.71	$89.70	$89.70
Purchase #7	$17.64	7.120%	$18.896	$18.90	$18.90	$18.90
7 purchase totals =	$725.68		$788.5837	$788.59	$788.60	$788.60