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	$153.50	12.331%	$172.4281	$172.43	$172.45	$172.40
Purchase #2	$160.32	12.822%	$180.8762	$180.88	$180.90	$180.90
Purchase #3	$247.41	13.550%	$280.9341	$280.93	$280.95	$280.90
Purchase #4	$248.72	11.230%	$276.6513	$276.65	$276.65	$276.70
Purchase #5	$69.65	10.398%	$76.8922	$76.89	$76.90	$76.90
Purchase #6	$67.73	3.601%	$70.169	$70.17	$70.15	$70.20
Purchase #7	$166.59	5.197%	$175.2477	$175.25	$175.25	$175.20
7 purchase totals =	$1,113.92		$1,233.1986	$1,233.20	$1,233.25	$1,233.20