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	$140.31	11.731%	$156.7698	$156.77	$156.75	$156.80
Purchase #2	$137.85	10.800%	$152.7378	$152.74	$152.75	$152.70
Purchase #3	$21.73	5.831%	$22.9971	$23.00	$23.00	$23.00
Purchase #4	$72.35	9.119%	$78.9476	$78.95	$78.95	$78.90
Purchase #5	$158.83	7.606%	$170.9106	$170.91	$170.90	$170.90
Purchase #6	$244.70	4.419%	$255.5133	$255.51	$255.50	$255.50
Purchase #7	$202.88	6.638%	$216.3472	$216.35	$216.35	$216.30
7 purchase totals =	$978.65		$1,054.2234	$1,054.23	$1,054.20	$1,054.10