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	$115.55	10.400%	$127.5672	$127.57	$127.55	$127.60
Purchase #2	$235.57	12.721%	$265.5369	$265.54	$265.55	$265.50
Purchase #3	$121.92	12.802%	$137.5282	$137.53	$137.55	$137.50
Purchase #4	$125.92	13.220%	$142.5666	$142.57	$142.55	$142.60
Purchase #5	$48.78	6.526%	$51.9634	$51.96	$51.95	$52.00
Purchase #6	$198.40	12.152%	$222.5096	$222.51	$222.50	$222.50
Purchase #7	$97.45	4.294%	$101.6345	$101.63	$101.65	$101.60
7 purchase totals =	$943.59		$1,049.3064	$1,049.31	$1,049.30	$1,049.30