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	$112.52	12.505%	$126.5906	$126.59	$126.60	$126.60
Purchase #2	$216.89	9.202%	$236.8482	$236.85	$236.85	$236.80
Purchase #3	$34.37	7.119%	$36.8168	$36.82	$36.80	$36.80
Purchase #4	$37.51	12.357%	$42.1451	$42.15	$42.15	$42.10
Purchase #5	$67.67	6.124%	$71.8141	$71.81	$71.80	$71.80
Purchase #6	$67.31	5.782%	$71.2019	$71.20	$71.20	$71.20
Purchase #7	$156.37	12.371%	$175.7145	$175.71	$175.70	$175.70
7 purchase totals =	$692.64		$761.1312	$761.13	$761.10	$761.00