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	$82.67	8.243%	$89.4845	$89.48	$89.50	$89.50
Purchase #2	$187.46	12.232%	$210.3901	$210.39	$210.40	$210.40
Purchase #3	$39.72	3.256%	$41.0133	$41.01	$41.00	$41.00
Purchase #4	$191.51	4.607%	$200.3329	$200.33	$200.35	$200.30
Purchase #5	$178.72	13.602%	$203.0295	$203.03	$203.05	$203.00
Purchase #6	$60.79	5.121%	$63.9031	$63.90	$63.90	$63.90
Purchase #7	$244.39	10.289%	$269.5353	$269.54	$269.55	$269.50
7 purchase totals =	$985.26		$1,077.6887	$1,077.68	$1,077.75	$1,077.60