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	$119.90	6.383%	$127.5532	$127.55	$127.55	$127.60
Purchase #2	$70.91	9.449%	$77.6103	$77.61	$77.60	$77.60
Purchase #3	$86.94	3.685%	$90.1437	$90.14	$90.15	$90.10
Purchase #4	$19.90	12.140%	$22.3159	$22.32	$22.30	$22.30
Purchase #5	$60.98	10.542%	$67.4085	$67.41	$67.40	$67.40
Purchase #6	$212.82	6.158%	$225.9255	$225.93	$225.95	$225.90
Purchase #7	$48.68	6.474%	$51.8315	$51.83	$51.85	$51.80
7 purchase totals =	$620.13		$662.7886	$662.79	$662.80	$662.70