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	$236.61	10.654%	$261.8184	$261.82	$261.80	$261.80
Purchase #2	$69.88	12.500%	$78.615	$78.62	$78.60	$78.60
Purchase #3	$155.68	11.668%	$173.8447	$173.84	$173.85	$173.80
Purchase #4	$229.31	6.422%	$244.0363	$244.04	$244.05	$244.00
Purchase #5	$238.37	8.822%	$259.399	$259.40	$259.40	$259.40
Purchase #6	$163.58	13.645%	$185.9005	$185.90	$185.90	$185.90
Purchase #7	$76.31	3.369%	$78.8809	$78.88	$78.90	$78.90
7 purchase totals =	$1,169.74		$1,282.4948	$1,282.50	$1,282.50	$1,282.40