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	$178.93	12.646%	$201.5575	$201.56	$201.55	$201.60
Purchase #2	$132.48	11.772%	$148.0755	$148.08	$148.10	$148.10
Purchase #3	$238.51	7.502%	$256.403	$256.40	$256.40	$256.40
Purchase #4	$240.28	7.172%	$257.5129	$257.51	$257.50	$257.50
Purchase #5	$137.66	13.175%	$155.7967	$155.80	$155.80	$155.80
Purchase #6	$134.99	4.654%	$141.2724	$141.27	$141.25	$141.30
Purchase #7	$162.64	6.304%	$172.8928	$172.89	$172.90	$172.90
7 purchase totals =	$1,225.49		$1,333.5108	$1,333.51	$1,333.50	$1,333.60