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	$204.75	11.602%	$228.5051	$228.51	$228.50	$228.50
Purchase #2	$23.45	8.368%	$25.4123	$25.41	$25.40	$25.40
Purchase #3	$229.34	9.204%	$250.4485	$250.45	$250.45	$250.40
Purchase #4	$158.49	12.682%	$178.5897	$178.59	$178.60	$178.60
Purchase #5	$49.86	9.390%	$54.5419	$54.54	$54.55	$54.50
Purchase #6	$200.81	11.253%	$223.4071	$223.41	$223.40	$223.40
Purchase #7	$192.88	8.278%	$208.8466	$208.85	$208.85	$208.80
7 purchase totals =	$1,059.58		$1,169.7512	$1,169.76	$1,169.75	$1,169.60