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	$158.63	13.648%	$180.2798	$180.28	$180.30	$180.30
Purchase #2	$212.57	13.796%	$241.8962	$241.90	$241.90	$241.90
Purchase #3	$93.71	12.506%	$105.4294	$105.43	$105.45	$105.40
Purchase #4	$34.39	6.667%	$36.6828	$36.68	$36.70	$36.70
Purchase #5	$111.77	7.117%	$119.7247	$119.72	$119.70	$119.70
Purchase #6	$189.76	13.781%	$215.9108	$215.91	$215.90	$215.90
Purchase #7	$163.57	9.181%	$178.5874	$178.59	$178.60	$178.60
7 purchase totals =	$964.40		$1,078.5111	$1,078.51	$1,078.55	$1,078.50