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	$159.30	4.537%	$166.5274	$166.53	$166.55	$166.50
Purchase #2	$79.39	3.373%	$82.0678	$82.07	$82.05	$82.10
Purchase #3	$61.57	9.588%	$67.4733	$67.47	$67.45	$67.50
Purchase #4	$84.26	4.413%	$87.9784	$87.98	$88.00	$88.00
Purchase #5	$160.68	12.376%	$180.5658	$180.57	$180.55	$180.60
Purchase #6	$87.72	3.546%	$90.8306	$90.83	$90.85	$90.80
Purchase #7	$231.97	8.603%	$251.9264	$251.93	$251.95	$251.90
7 purchase totals =	$864.89		$927.3697	$927.38	$927.40	$927.40