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	$226.60	12.510%	$254.9477	$254.95	$254.95	$254.90
Purchase #2	$81.59	10.223%	$89.9309	$89.93	$89.95	$89.90
Purchase #3	$62.27	8.873%	$67.7952	$67.80	$67.80	$67.80
Purchase #4	$125.67	9.235%	$137.2756	$137.28	$137.30	$137.30
Purchase #5	$209.39	12.738%	$236.0621	$236.06	$236.05	$236.10
Purchase #6	$33.47	8.748%	$36.398	$36.40	$36.40	$36.40
Purchase #7	$59.79	4.590%	$62.5344	$62.53	$62.55	$62.50
7 purchase totals =	$798.78		$884.9439	$884.95	$885.00	$884.90