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	$226.43	4.318%	$236.2072	$236.21	$236.20	$236.20
Purchase #2	$49.45	9.343%	$54.0701	$54.07	$54.05	$54.10
Purchase #3	$231.72	10.772%	$256.6809	$256.68	$256.70	$256.70
Purchase #4	$97.72	5.158%	$102.7604	$102.76	$102.75	$102.80
Purchase #5	$52.59	7.796%	$56.6899	$56.69	$56.70	$56.70
Purchase #6	$158.34	6.444%	$168.5434	$168.54	$168.55	$168.50
Purchase #7	$242.31	11.614%	$270.4519	$270.45	$270.45	$270.50
7 purchase totals =	$1,058.56		$1,145.4038	$1,145.40	$1,145.40	$1,145.50