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	$72.55	11.726%	$81.0572	$81.06	$81.05	$81.10
Purchase #2	$87.30	8.734%	$94.9248	$94.92	$94.90	$94.90
Purchase #3	$59.55	4.513%	$62.2375	$62.24	$62.25	$62.20
Purchase #4	$202.65	11.282%	$225.513	$225.51	$225.50	$225.50
Purchase #5	$174.55	6.213%	$185.3948	$185.39	$185.40	$185.40
Purchase #6	$128.46	7.368%	$137.9249	$137.92	$137.90	$137.90
Purchase #7	$239.32	7.567%	$257.4293	$257.43	$257.45	$257.40
7 purchase totals =	$964.38		$1,044.4815	$1,044.47	$1,044.45	$1,044.40