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	$134.89	7.161%	$144.5495	$144.55	$144.55	$144.50
Purchase #2	$100.70	9.164%	$109.9281	$109.93	$109.95	$109.90
Purchase #3	$59.66	13.719%	$67.8448	$67.84	$67.85	$67.80
Purchase #4	$158.35	13.530%	$179.7748	$179.77	$179.75	$179.80
Purchase #5	$244.62	13.202%	$276.9147	$276.91	$276.90	$276.90
Purchase #6	$226.62	6.127%	$240.505	$240.51	$240.50	$240.50
Purchase #7	$218.94	10.499%	$241.9265	$241.93	$241.95	$241.90
7 purchase totals =	$1,143.78		$1,261.4434	$1,261.44	$1,261.45	$1,261.30