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	$212.72	4.538%	$222.3732	$222.37	$222.35	$222.40
Purchase #2	$146.64	5.740%	$155.0571	$155.06	$155.05	$155.10
Purchase #3	$236.64	9.565%	$259.2746	$259.27	$259.25	$259.30
Purchase #4	$196.47	11.434%	$218.9344	$218.93	$218.95	$218.90
Purchase #5	$17.42	12.116%	$19.5306	$19.53	$19.55	$19.50
Purchase #6	$138.90	8.566%	$150.7982	$150.80	$150.80	$150.80
Purchase #7	$155.82	11.537%	$173.797	$173.80	$173.80	$173.80
7 purchase totals =	$1,104.61		$1,199.7651	$1,199.76	$1,199.75	$1,199.80