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	$98.59	13.402%	$111.803	$111.80	$111.80	$111.80
Purchase #2	$175.55	9.200%	$191.7006	$191.70	$191.70	$191.70
Purchase #3	$204.66	4.755%	$214.3916	$214.39	$214.40	$214.40
Purchase #4	$105.82	7.719%	$113.9882	$113.99	$114.00	$114.00
Purchase #5	$209.74	7.662%	$225.8103	$225.81	$225.80	$225.80
Purchase #6	$37.28	4.342%	$38.8987	$38.90	$38.90	$38.90
Purchase #7	$178.77	12.157%	$200.5031	$200.50	$200.50	$200.50
7 purchase totals =	$1,010.41		$1,097.0955	$1,097.09	$1,097.10	$1,097.10