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	$169.65	12.773%	$191.3194	$191.32	$191.30	$191.30
Purchase #2	$145.71	5.389%	$153.5623	$153.56	$153.55	$153.60
Purchase #3	$136.54	4.682%	$142.9328	$142.93	$142.95	$142.90
Purchase #4	$66.47	6.118%	$70.5366	$70.54	$70.55	$70.50
Purchase #5	$235.81	12.469%	$265.2131	$265.21	$265.20	$265.20
Purchase #6	$56.94	4.416%	$59.4545	$59.45	$59.45	$59.50
Purchase #7	$239.76	9.214%	$261.8515	$261.85	$261.85	$261.90
7 purchase totals =	$1,050.88		$1,144.8702	$1,144.86	$1,144.85	$1,144.90