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	$22.98	3.796%	$23.8523	$23.85	$23.85	$23.90
Purchase #2	$64.85	3.774%	$67.2974	$67.30	$67.30	$67.30
Purchase #3	$69.67	12.855%	$78.6261	$78.63	$78.65	$78.60
Purchase #4	$67.47	5.748%	$71.3482	$71.35	$71.35	$71.30
Purchase #5	$78.31	8.502%	$84.9679	$84.97	$84.95	$85.00
Purchase #6	$29.72	7.458%	$31.9365	$31.94	$31.95	$31.90
Purchase #7	$146.50	13.849%	$166.7888	$166.79	$166.80	$166.80
7 purchase totals =	$479.50		$524.8172	$524.83	$524.85	$524.80