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	$76.72	11.565%	$85.5927	$85.59	$85.60	$85.60
Purchase #2	$118.33	13.205%	$133.9555	$133.96	$133.95	$134.00
Purchase #3	$163.75	6.767%	$174.831	$174.83	$174.85	$174.80
Purchase #4	$247.35	3.443%	$255.8663	$255.87	$255.85	$255.90
Purchase #5	$244.31	9.136%	$266.6302	$266.63	$266.65	$266.60
Purchase #6	$210.75	3.850%	$218.8639	$218.86	$218.85	$218.90
Purchase #7	$129.37	9.547%	$141.721	$141.72	$141.70	$141.70
7 purchase totals =	$1,190.58		$1,277.4606	$1,277.46	$1,277.45	$1,277.50