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	$128.38	7.172%	$137.5874	$137.59	$137.60	$137.60
Purchase #2	$115.83	10.511%	$128.0049	$128.00	$128.00	$128.00
Purchase #3	$87.61	4.613%	$91.6514	$91.65	$91.65	$91.70
Purchase #4	$204.55	4.447%	$213.6463	$213.65	$213.65	$213.60
Purchase #5	$121.87	7.759%	$131.3259	$131.33	$131.35	$131.30
Purchase #6	$174.82	9.270%	$191.0258	$191.03	$191.05	$191.00
Purchase #7	$42.68	13.103%	$48.2724	$48.27	$48.25	$48.30
7 purchase totals =	$875.74		$941.5141	$941.52	$941.55	$941.50