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	$242.47	13.261%	$274.6239	$274.62	$274.60	$274.60
Purchase #2	$246.86	12.422%	$277.5249	$277.52	$277.50	$277.50
Purchase #3	$162.25	3.714%	$168.276	$168.28	$168.30	$168.30
Purchase #4	$75.48	3.262%	$77.9422	$77.94	$77.95	$77.90
Purchase #5	$121.50	8.555%	$131.8943	$131.89	$131.90	$131.90
Purchase #6	$101.69	4.655%	$106.4237	$106.42	$106.40	$106.40
Purchase #7	$17.49	11.835%	$19.5599	$19.56	$19.55	$19.60
7 purchase totals =	$967.74		$1,056.2449	$1,056.23	$1,056.20	$1,056.20