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	$100.58	7.720%	$108.3448	$108.34	$108.35	$108.30
Purchase #2	$174.78	9.661%	$191.6655	$191.67	$191.65	$191.70
Purchase #3	$31.89	5.496%	$33.6427	$33.64	$33.65	$33.60
Purchase #4	$152.57	9.199%	$166.6049	$166.60	$166.60	$166.60
Purchase #5	$33.66	3.130%	$34.7136	$34.71	$34.70	$34.70
Purchase #6	$122.28	12.390%	$137.4305	$137.43	$137.45	$137.40
Purchase #7	$19.27	11.417%	$21.4701	$21.47	$21.45	$21.50
7 purchase totals =	$635.03		$693.8721	$693.86	$693.85	$693.80