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	$47.91	12.514%	$53.9055	$53.91	$53.90	$53.90
Purchase #2	$194.35	11.318%	$216.3465	$216.35	$216.35	$216.30
Purchase #3	$76.29	13.474%	$86.5693	$86.57	$86.55	$86.60
Purchase #4	$95.59	11.499%	$106.5819	$106.58	$106.60	$106.60
Purchase #5	$226.95	12.451%	$255.2075	$255.21	$255.20	$255.20
Purchase #6	$39.32	11.304%	$43.7647	$43.76	$43.75	$43.80
Purchase #7	$234.30	13.626%	$266.2257	$266.23	$266.25	$266.20
7 purchase totals =	$914.71		$1,028.6011	$1,028.61	$1,028.60	$1,028.60