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	$141.28	3.382%	$146.0581	$146.06	$146.05	$146.10
Purchase #2	$34.41	10.356%	$37.9735	$37.97	$37.95	$38.00
Purchase #3	$237.31	9.320%	$259.4273	$259.43	$259.45	$259.40
Purchase #4	$53.88	3.683%	$55.8644	$55.86	$55.85	$55.90
Purchase #5	$226.93	9.847%	$249.2758	$249.28	$249.30	$249.30
Purchase #6	$142.98	6.223%	$151.8776	$151.88	$151.90	$151.90
Purchase #7	$62.71	3.126%	$64.6703	$64.67	$64.65	$64.70
7 purchase totals =	$899.50		$965.1470	$965.15	$965.15	$965.30