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	$41.78	7.460%	$44.8968	$44.90	$44.90	$44.90
Purchase #2	$205.87	3.326%	$212.7172	$212.72	$212.70	$212.70
Purchase #3	$118.33	7.548%	$127.2615	$127.26	$127.25	$127.30
Purchase #4	$138.51	6.519%	$147.5395	$147.54	$147.55	$147.50
Purchase #5	$70.40	13.497%	$79.9019	$79.90	$79.90	$79.90
Purchase #6	$41.80	13.647%	$47.5044	$47.50	$47.50	$47.50
Purchase #7	$168.79	9.278%	$184.4503	$184.45	$184.45	$184.50
7 purchase totals =	$785.48		$844.2716	$844.27	$844.25	$844.30