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	$245.97	3.818%	$255.3611	$255.36	$255.35	$255.40
Purchase #2	$168.51	3.169%	$173.8501	$173.85	$173.85	$173.90
Purchase #3	$200.95	12.142%	$225.3493	$225.35	$225.35	$225.30
Purchase #4	$194.62	11.433%	$216.8709	$216.87	$216.85	$216.90
Purchase #5	$203.81	9.718%	$223.6163	$223.62	$223.60	$223.60
Purchase #6	$187.56	6.741%	$200.2034	$200.20	$200.20	$200.20
Purchase #7	$14.25	11.476%	$15.8853	$15.89	$15.90	$15.90
7 purchase totals =	$1,215.67		$1,311.1364	$1,311.14	$1,311.10	$1,311.20