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	$213.91	7.278%	$229.4784	$229.48	$229.50	$229.50
Purchase #2	$28.90	13.194%	$32.7131	$32.71	$32.70	$32.70
Purchase #3	$243.59	12.588%	$274.2531	$274.25	$274.25	$274.30
Purchase #4	$235.37	4.340%	$245.5851	$245.59	$245.60	$245.60
Purchase #5	$167.33	3.721%	$173.5563	$173.56	$173.55	$173.60
Purchase #6	$102.97	4.722%	$107.8322	$107.83	$107.85	$107.80
Purchase #7	$48.51	5.123%	$50.9952	$51.00	$51.00	$51.00
7 purchase totals =	$1,040.58		$1,114.4134	$1,114.42	$1,114.45	$1,114.50